From Atrophy to Rocket Science (and back): A Brief History of Property Assessments in Allegheny County

Christopher Briem
25 min readJul 18, 2022


An abridged version of this was published on PublicSource on July 19, 2022

Property assessments in Allegheny County are again in the news. As reported by PublicSource, a group of local homeowners is currently challenging the county’s administration of the property assessment system. The legal wrangling is far from new. The case is just the latest iteration of direct judicial intervention in Allegheny County’s property tax assessment system, now going back half a century.

Few are ever happy with their property tax bills. Property taxes are by far the most common source of revenue for local governments across not just Pennsylvania but the nation. Most Pennsylvania homeowners pay property taxes to their county of residence, local municipality, and school district. Tax bills are determined by local millage rates set by each jurisdiction and the assessed value of each parcel of real estate. Though millage rates may be uniform across a jurisdiction, the underlying property values vary widely, generating widely different tax bills for property owners.

Allegheny County Property Assessment Web Page

Property owners can easily be confused by the tax bills they receive, often based on property values that seemingly have little to do with the current market value of their homes. Allegheny County assessments currently use a 2012 base year system, reflecting the last year a county-wide comprehensive evaluation of all properties was completed. Over the subsequent decade, real estate market prices have not remained static, but there has been no mass reassessment of property since then. Where assessed values — and thus tax bills — have changed, adjustments have mostly resulted from individual ad-hoc appeals, appeals sought either by homeowners themselves or local jurisdictions that can initiate proceedings before the Allegheny County Board of Property Assessments Appeals and Review (BPAAR).

Pittsburgh Press photo of property assessment protest, November 18, 1930

If property values were assessed fairly, and if all property values changed at the same rate over time, there would be little need to reassess values for tax purposes. Base year valuations may reflect past property values, but if the change over time was uniform, then the effective tax rates facing homeowners would remain the same. But real estate markets are anything but static, and different communities within the county have experienced widely varying economic trends which are reflected in market prices. As those trends continue, the gap between a property’s assessed value and its market value only widens, and disparities across the county increase.

Pennsylvania has little standing legislation that requires counties to reassess properties on any schedule, and most counties rely on assessments dated by years, if not decades. Though it conducted a reassessment in 2017, Blair County in Pennsylvania, home to Altoona, used a 1958 base year assessment for nearly six decades. Many other Pennsylvania counties still rely on property valuation decades out of date. The lack of regular and recurring reassessments in Pennsylvania stands out even compared to its nearest neighbors. Ohio requires counties to reassess all properties at least once every six years and to adjust values for inflation every three years. In Maryland, state government-appointed assessors conduct a mass assessment of all properties every three years.

Lacking similar mandates in Pennsylvania statutes, there is little uniformity in how long counties in Pennsylvania can go before they undertake any systematic reassessment. Allegheny County’s current 2012 base year assessment only happened because of litigation brought before the Allegheny County Court of Common Pleas. Multiple plaintiffs argued that inequities in assessed values had grown over the decade since the previous mass reassessment. It was only a ruling by then Senior Judge R. Stanton Wettick that forced the county to conduct the most recent reassessment. A decade earlier, it was a similar judicial intervention, also overseen by Judge Wettick, that forced the county to conduct reassessments of all properties in Allegheny County in both 2001 and 2002, the first such mass reassessments in decades.

Property assessments in Allegheny County were not always subject to judicial intervention. From the very beginning of the commonwealth, townships elected assessors responsible for assessing the value of properties. Property taxes have always been the primary source of revenue for both local municipalities and school districts. At various points in the 19th century, homeowners even had to pay a separate property tax levied by Pennsylvania’s state government.

Through the 19th century and into the 1940s, Allegheny County performed triennial assessments where all properties were reassessed every third year. Historical assessments typically added up not only the value of real estate, including the value of land and structures but also the value of other personal property, which was also taxed annually, much akin to a wealth tax.

In 1939, Pennsylvania passed a new Second Class County Assessment Law, which only applied to Allegheny County. The law required the previously separate city of Pittsburgh and Allegheny County assessment boards to be combined, and in 1944 the county began a new schedule for property assessments.[1] A triennial assessment system would be kept in place, but instead of all properties being assessed every third year, a third of all properties would be reassessed each year. This cycle of assessments remained in place through most of the subsequent four decades with minimal controversy.

Ironically it was not a lack of regular reassessments that spurred the courts to intervene in Allegheny County but complaints that the triennial system meant that some assessments were one, or at most two years out of the cycle. Pennsylvania’s state constitution includes a strict uniformity clause that requires equal taxation on all taxpayers. The triennial assessment system meant that three different assessments were in effect in any given year, an inconsistency that would eventually be tested in court.

This lack of uniformity was at least nominally the reason the borough of Green Tree sued Allegheny County over its assessment practices in 1970, but a wider range of complaints about the county’s assessment system were growing. While the case lingered, in 1974, the Allegheny County commissioners appointed a commission to study the state of property assessments in Allegheny County. Headed by county solicitor Alex Jaffurs, the commission produced as comprehensive an evaluation of Allegheny County property assessment practices as has ever been written, before or since.

The largest problem identified by the Jaffurs report was the lack of current or even consistent real estate data. The core data individual assessors used included depression-era line drawings of properties that had not been updated since the 1930s. The report’s overarching recommendation was that the county’s assessment methodology needed comprehensive modernization. Not just did the county lack sufficient data to accurately set assessment values, but most assessments were conducted by a small army of county assessors who used their individual and inconsistent methods to set valuations.

In 1977 the borough of Wilkinsburg filed a similar suit against county assessment practices, which was consolidated with the lingering case brought by Green Tree before Allegheny County Court of Common Pleas Judge Nicholas Papakados, who had been elected in 1975. He directed the end of the triennial assessment system in 1978 and then took the unprecedented step of crafting a consent decree with the county which placed him in direct control of the county assessor’s office.

Photo of Judge Nicholas Papadakos
Judge Nicholas Papadakos

While practices in Allegheny County were not atypical of how governments conducted property assessments elsewhere, there was an emerging role for computer-assisted mass appraisal (CAMA) software. One of the first programs to assist assessors was distributed by the Lincoln Institute of Land Policy, a Cambridge, Massachusetts, think tank originally founded to promote the ideas of 19th-century economist Henry George and the land tax. In the early 1980s, the Lincoln Institute developed software called SOLIR (Small On-LIne Research), which ran on a common Radio Shack TRS-80 computer to assist local assessors set real estate values for tax purposes.[2]

As archaic as its processes were at the same time, Allegheny County was on a path to becoming a national leader in assessment practices. Based on the recommendations of the Jaffurs’ report, Allegheny County issued an RFP to find the best computer models to be used to set property values. In 1978, seven firms were provided a dataset with real-world information on the characteristics of 3,500 recently sold properties, but the firms were only told the actual sales prices for 2,800 of the transactions. The firms were evaluated on how accurately they estimated the sales prices of the remaining 700 properties.[3]

The team that outperformed all others — including many long-established real estate firms — was made up of two local researchers who had developed a new computer model to predict property values. The team included Richard Longini, a professor of Electrical Engineering at Carnegie Mellon University (CMU) and who had a secondary appointment as a professor at CMU’s School of Urban Affairs. Longini and former CMU graduate student Robert Carbone had applied more sophisticated statistical techniques than those typically used in early CAMA models.

The model developed out of Carbone’s 1975 dissertation research with Professor Longini whose curiosity over his home’s assessed value led him to expand his research portfolio far outside his traditional research. I had the chance to meet with Professor Longini in the 1990s and he explained to me he was he was not upset, but more confused by the valuation his Squirrel Hill home was given by county property assessors. The valuation set by the county determined what property tax was owed not just to the county but for larger property tax bills owed to the city of Pittsburgh and the Pittsburgh School District. He queried the county on their methodology.


Longini had a Ph.D. in physics from the University of Pittsburgh and had a 28-year career in industrial electronic research before joining the faculty of Carnegie Tech in 1962. His previous research focused on quantum mechanics and the solid-state physics of transistors — the alchemy that underlies all things digital in the modern world. As was inevitable, the county’s response was unfulfilling and likely came nowhere near the rigor he applied in his engineering research.

Richard Longini at Westinghouse Laboratories, 1948

How did they outperform so many established competitors in predicting sales values in Allegheny County? The early computer models used to set market values, models such as the Lincoln Institute’s SOLIR model, relied mostly on what is called multiple regression analysis. Regression is a standard statistical technique that can be used to decompose individual property values into how much total value can be attributable to individual parcel characteristics, for example, a property’s total size, the number of rooms, and overall condition. As implemented in early assessment models, multiple regression analysis would have typically been a cross-sectional analysis, looking at a set of the most recent real estate sales data, decomposing those values into how much is contributed by each characteristic, and then applying those values to set assessment values for all properties whether they had been sold recently or not.

Going beyond basic regression methods, Longini and Carbone proposed a more sophisticated statistical technique called an adaptive estimation procedure (AEP) to predict real estate prices. Also called feedback models, AEP techniques implement an iterative, self-referential algorithm that not only looks not just at the most recent sales data but evaluates historic price trends to estimate current real estate values. It was a technique that had been developed decades earlier but had become more widely used after World War II in early rocketry and orbital mechanics where it was used to track the movement of satellites and ballistic launch vehicles.[4] AEP used the techniques of multiple regression analysis, but it also evaluated the error in its projections using previous sales data, and those past errors were fed back into the calculation of current market values.[5]

A major challenge in property assessments, then and now, is that the number of “arm’s length” real estate sales in a given year can be very limited compared to the total number of parcels that need to be assessed for tax purposes. CAMA models must set the values of a large number of parcels based on recent sales data based on sales data from just a small fraction of properties. The problem is compounded by the fact that some recorded transaction values, such as purchases between family members, do not reflect market values.

Computer models deal with the sparseness of recent sales data by either expanding the geography to use for comparable sales or by aggregating sales data from a more extended period of time into the past, but each technique has its drawbacks. The larger the geographic area used for a specific model, the less comparable groups of properties are, but more sales data is available on recent sales. Grouping more historical data together in a simple regression model gives the model more sales data to work with but might not capture recent price trends. Because the feedback model Longini and Carbone devised was designed to take advantage of sales data going back several years, it had more data to work with and proved more accurate than techniques based solely on regression analysis or individual assessments made by professional assessors.

For Allegheny County, the feedback model uniquely used by Longini and Carbone proved faster and at least as accurate as the techniques used by other firms in the 1978 competition. In a sense, their algorithm was ideal for the hard-to-assess landscape of Allegheny County, where the geography of comparable sales needs to be relatively small because property values of similar homes can vary neighborhood by neighborhood in ways seemingly inconsistent with physical geography.

Longini and Carbone along with local real estate broker Ed Ivory formed a small firm to market property assessment software based on the “feedback” model they applied to real estate forecasting. Based on their success with 1978 data, Allegheny County purchased the software for $79,000 — the equivalent of $350,000 in 2022 — and began work to build the comprehensive county-wide database that was needed to implement a CAMA-based reassessment of all properties.[6]

New computer software was just one part of a successful reassessment. Though Allegheny County has purchased the Longini-Carbone software, implementing a full CAMA-based reassessment was not possible until consistent data was compiled for the nearly 600 thousand individual parcels across the county, a huge task given that most data would need to be compiled from scratch. No comprehensive data on the characteristics of all real estate parcels had existed since the county was first divided into a block and lot system in 1945. At the end of the 1970s, the county did not even maintain a common record card of information on individual parcels that was used by all assessors. Building the required database would be an enormous and costly task.

If it had gone forward, estimated costs to collect all the data required to complete a full reassessment ranged from $3–10 million, or the equivalent of $10–40 million in 2022. While not an extraordinary expense for a large county, the new assessment would have taken place just as economic shocks were growing larger. The first of two back-to-back economic recessions began in January 1980 and had disproportionate impacts in southwestern Pennsylvania, putting unprecedented stresses on public finances

Due to the scale of the anticipated costs, pushback from county assessors, or other reasons, the project to build a comprehensive database of real estate in the county was never completed or, at the very least, not maintained for very long into the future. Efforts at reforming the Allegheny County assessment went into a semi-permanent stasis once Judge Papadakos formally ended his oversight of the county’s assessment bureaucracy in 1982 and soon thereafter elected to the state supreme court in 1983.

The software would remain at most minimally used, if at all. Decades later, Professor Longini told me that there was tremendous pushback from the staff of roughly 70 county assessors because of the threat it posed to their jobs.[7] What need would there be for the services of so many assessors if a computer could quickly and presumably more consistently set assessment values?

The “feedback” software became the primary product of EDA Feedback, Inc., the company originally formed to provide assessment software to Allegheny County. But the methodology proved to be effective elsewhere. At some point in the 1980s, the company was sold to one of its larger clients, the property assessor of Pinellas County, Florida who continued to market the software nationwide.[8]

In the early 1990s, the Pittsburgh Post-Gazette began reporting on the growing inaccuracies in Allegheny County assessments. An investigative series in1994 documented the scale of discrepancies between recent sales prices and assessed values. By then, any centralized real estate data maintained by the county had become ever more deprecated and assessments continued to be determined mostly by individual assessors using incomplete data, a practice criticized by the Jaffurs’ report nearly two decades earlier.

At the time, results from the feedback model were made available to Allegheny County assessors, but more widely used were estimates from an alternative computer model named ALGO developed by a State College, PA consultant.[9] But neither computer model had much hope of generating accurate results given the lack of comprehensive data maintained by the county. Seemingly in response to the negative press coverage, the county made a large effort to reset assessment values in 1994, but the results only created ever greater public outrage and calls for reform of the entire assessment system.

Assessment practices in the county were soon transformed by more significant political shifts taking place in Allegheny County. Since the county was first cleaved from Washington and Westmoreland Counties in 1788, Allegheny County had been governed by a three-member commissioner system that acted as both executive and legislative bodies. For six decades, the Democratic Party had successfully elected two of the three county commissioners, but in 1996 two Republicans, Larry Dunn and Bob Cranmer were elected and took control of Allegheny County government. One of their first acts was to freeze all county assessments, effectively halting reassessments and even stopping most ongoing appeals. Then they went so far as to lay off virtually the entire staff of county assessors as the county faced a budget crisis, a crisis much of their making as they had also unilaterally cut county property taxes by 20 percent upon taking office.

The assessment freeze soon prompted yet another lawsuit against Allegheny County over its assessment practices. Judge Stanton Wettick was assigned the case and would be central to the fate of assessments in Allegheny County for much of the next two decades. While he would never assume the role Judge Papadakos did as de facto county assessment manager, he would be the catalyst for more lasting change.

Judge R. Stanton Wettick (

Before the end of 1996, the county tried to recall its laid-off assessors but was also forced to contract with a private firm to manage the county’s assessment office. A contract was awarded to Sabre Systems, an Ohio-based firm that had been in the business of mass assessment for decades. Ironically, Sabre Systems had even been a bidder when Allegheny County issued its 1978 RFP, only to lose the work to Longini and Carbone’s novel software. In 1998 Wettick ordered Allegheny County to prepare to conduct its first comprehensive mass reassessment in decades which would be the county’s first to be based on CAMA models.

Almost simultaneously, even larger historic shifts were taking place in the governance of Allegheny County. County politics became ever more muddled as the coalition of Republicans Dunn and Cranmer frayed. Though they were of different parties, by 1998, Cranmer was allied with Democratic commissioner Mike Dawida to effectively govern the county. But soon the historic county commissioner system would be replaced altogether.

Decades of efforts to reform Allegheny County government had led up to a 1998 referendum asking voters if they wanted to approve a new home rule charter which passed by the narrowest of margins (50.1% — 49.9%) in the spring of 1998. The referendum ended the three-commissioner system and directed the election of a single elected Allegheny County executive and the creation of a new 15-member county council. Republican Jim Roddey was elected as the first county chief executive and took office in January 2000 as the court-ordered reassessment process was ongoing.

Following rulings from Judge Wettick, the county again issued an RFP seeking firms to set new property valuations across the counties. The project was expected to be both complicated and expensive by the need to build virtually from scratch a database of the characteristics of all county properties — the county still having never followed the recommendations noted by the Jaffurs’ report a quarter-century earlier. Not only did property valuations need to be set, but virtually all of the core data had to be collected and prepared for the use of now widely-used CAMA models to set assessment values.

A $24 million contract was awarded to Sabre Systems to complete the reassessment, but Sabre did something different than what it normally did for assessments in Ohio or other states. Sabre managed the whole process of collecting data and building a database needed for CAMA models, but it subcontracted the actual modeling of prices to EDA Feedback Inc., the firm that Richard Longini, Robert Carbone, and Ed Ivory formed to implement CAMA modeling for Allegheny County in 1979. In essence, Allegheny County was paying for software it already owned and had tested.

Not only that, but the manager Sabre Systems hired for its work in Allegheny County was George Donatello, the general manager of EDA Feedback Inc., who had previously managed the Citrus County, Florida assessor’s office. Donatello’s boss, Citrus County chief assessor George Schulz had purchased the software company while he was Chief Assessor of Pinellas County, Florida, but had moved and later was elected the chief assessor of Citrus County, Florida.[10]

New assessment values were completed in 2000 for use with 2001 tax bills. When made public, the new valuations were a shock to most homeowners who had not seen few adjustments to their assessed values in decades. But there was a problem with the numbers that exacerbated the shock. Property values across the county varied widely, and many estimated values did not seem to match market values as was the goal. Some errors can be expected in setting the market value of so many properties, but there was a pattern to the errors. There was an obvious imbalance in the assessment values, with lower-valued communities seemingly assessed above market values. As a result, in 2001, the Mon Valley Unemployment Committee (MVUC) sued the county over inequitable assessment values across the county. MVUC was represented by Don Driscoll of the Community Justice Project, a local nonprofit that had been spun out of Neighborhood Legal Services.

Judge Wettick directed that a local consulting firm be brought to evaluate the completed assessment and oversee a similar reassessment the following year. CONSAD, a firm based in the City of Pittsburgh’s East Liberty neighborhood, concluded that the feedback software used by Sabre Systems worked properly, but found several problems with how Sabre Systems applied the software in reassessing properties in Allegheny County. The county had been divided into just 12 market subareas, which CONSAD considered too few to distinguish the many real estate submarkets within Allegheny County. CONSAD also suggested that the county’s abandonment of its GIS program years earlier, another result of the Dunn-Cranmer election in 1996 and subsequent county budget crisis, hampered the county’s ability to effectively define real estate market areas. But the largest problem may have been something that CONSAD mentioned almost in passing. In calibrating the computer models, Sabre Systems had excluded all sales transactions under $10,000 from the model calibration.[11]

In Allegheny County at the time, many communities had extremely low property values that proved difficult to assess. A common practice in other parts of the country would be to exclude extremely low transaction values from computer modeling for assessment purposes. Extremely low values were often assumed to be transfers between family members or other forms of non- “arms-length” transactions that do not reflect market values. But in the 2000 reassessment, which was based on sales data through 2019, Sabre Systems had not made any distinction between low-value transactions that likely reflected market values and those that did not.

At the end of the 20th century, the Pittsburgh region had long experienced one of the lowest rates of real estate appreciation for decades. In many local communities, market values were indeed extremely low and many real estate transactions under $10,000 reflected market prices that should have been used in a CAMA model. In certain communities it could even have been argued there were concentrations of properties where the real value of many real estate parcels was negative, something evidenced by the high rate of property abandonment and vacancies in many municipalities. Systematically excluding these low-value transactions created a very predictable and inequitable bias in the CAMA-based results. Higher valued homes were systematically under-assessed while lower valued homes received higher assessments than they deserved.

There was additional fallout from the public’s shock over the new assessment values. The City of Pittsburgh and the City of Clairton were two Allegheny County municipalities that were using versions of a land tax to collect property tax. A land tax is a version of property tax championed by 19th-century economist Henry George. Under a land tax, the total value of a property is split between the value of land and the value of structures built there. George advocated for all property tax burden to fall on the value of land, and none on the value of structures. The land tax was theorized to inhibit land speculation and encourage denser property development.

The alternative version of the property tax, more common not only across Allegheny County but also across the nation is a flat property tax where the value of land and structures were taxed at the same rate. Most often, assessment values did not even need to make a distinction between the two. Pittsburgh maintained a ‘tiered’ tax which was very close to a true land tax. Land in the city of Pittsburgh was notionally taxed at a rate over five times higher than the tax rate for structures.

When the 2001 assessment values were made public, the impact of the land tax angered property owners in parts of the cities where land was more valuable. It is likely that past assessment practices had not accurately determined the split between the value of land and the value of structures, minimizing the impact of the tiered tax structure for residential property owners. The new assessment values made a more accurate determination of land values and, in certain neighborhoods would have immediately generated significant increases in property taxes. Though the city of Pittsburgh had used versions of a land tax since 1916, public anger prompted city politicians to quickly revamp tax policies and Pittsburgh reverted to a flat tax in 2001.

Sabre Systems would not be retained. A new contractor also based in Ohio, CLT Systems, would be hired to complete the follow-on assessment in 2001, for use in 2002 tax bills. Using an entirely different computer model, not the feedback model originally developed by Professors Longini and Carbone, new values were again assigned to every parcel in the county. Even that process was not well explained to the public and many were shocked to find out that any values set in appeals of the 2001 values were not used in setting the 2002 values.

Over continuing county objections, the 2002 assessment was completed and used for 2003 tax bills. The new values corrected at least some of the inequities that had existed in the previous assessment. The county planned to complete future assessments on a new three-year schedule. Yet again, local politics had more to say about the assessment practices in the county. Public anger at the incessant problems in the assessment system was at least partially responsible for Jim Roddey — the first elected Allegheny County Chief Executive — losing his race for re-election in the fall of 2003.

The county under newly elected county executive Dan Onorato completed a new assessment in 2005 to be used for 2006 tax bills, but the new values would never be used. The fear of public anger at yet another round of new values prompted County Executive Onorato to not certify the results. The values updated in 2005 were effectively abandoned and the county announced it would continue to rely on the 2002 assessment values into the future and the county canceled plans for future reassessments.

The effective freeze on assessments soon catalyzed new lawsuits from multiple parties against the county. A group of Squirrel Hill residents were represented by Ira Weiss, who also served as counsel to the Pittsburgh School District, while another set of residents was represented by Don Driscoll and the Community Justice Project which had sued the county following the 2000 reassessment. Again, the multiple lawsuits were consolidated before Judge Wettick, by then officially retired but serving as a senior judge in the Allegheny County Court of Common Pleas.

In 2007, Judge Wettick issued a ruling that the continued use of a base-year assessment system was unconstitutional due to the uniformity clause in the Pennsylvania constitution and he ordered a new county-wide reassessment to be completed. Following inevitable appeals, the Pennsylvania Supreme Court eventually issued a conflicted ruling in 2009 that affirmed the need for single new reassessment in Allegheny County, as ordered by Judge Wettick, but did not extend the ruling to any other Pennsylvania counties, or even into the future for Allegheny County.[11]

The legal process that moved forward had its humorous episodes as the county continued to argue against the need for any new mass reassessment, and worked to delay its completion. At one point, the county lacked a chief assessment officer. Judge Wettick ordered the county to hire a new chief assessment officer, and the county complied by hiring an experienced assessor living outside Chicago and who only came to Pittsburgh “every two weeks or as needed.” The county failed to produce a plan for a new assessment by the end of 2009, as ordered by the court. Then the county argued that a new assessment could not be completed until 2013, a plan the judge ruled was not acceptable.

While the assessment litigation was ongoing, Allegheny County Executive Dan Onorato ran for governor of Pennsylvania in 2010. He won the Democratic primary but was defeated in the general election that year. He announced he would not seek a third term in county office. Allegheny County Council President Rich Fitzgerald was elected Allegheny County Chief Executive in January of 2012 as the new assessment was being completed. The new chief executive continued the county’s opposition to the new assessment, prompting Judge Wettick to effectively order top county employees to ignore his direction and complete the assessment that year.

New assessment values were eventually completed by yet another contractor, Tyler Technologies Inc., and were used for 2013 tax bills. But no plan was put in place to complete any future reassessment. Allegheny County announced it would continue to use the 2012 values as its “base year” for tax purposes indefinitely into the future, a practice still widely used across Pennsylvania. Though Judge Wettick had ruled the use of base-year assessments unconstitutional, the Pennsylvania Supreme Court had limited his ruling to just the continued use of Allegheny County’s 2002 base-year assessment. Not only did the supreme court limit the impact of Judge Wettick’s ruling to Allegheny County, it did not even preclude the county from reverting back to using a base-year assessment once a single new reassessment was completed.[12]

Judge Wettick’s order to complete a new Allegheny County mass assessment in 2012

Which brings us back to the present day and again a full decade has passed since the last complete reassessment in Allegheny County. While the county continues to use assessment values set in 2012, that does not mean assessment values for all property owners have stayed the same. Taxing jurisdictions such as municipalities and school districts have the right to appeal individual property values even without the consent of property owners. Several thousand individual appeals are pending before the BPAAR, the appointed independent commission that adjudicates assessment appeals.

Because county assessments are currently based on 2012 values, the fact that a property’s market value has increased over time is not sufficient to cause tax bills to increase. However, if a property’s market value has appreciated faster than the average appreciation across the county, there is the potential the appeals process can set a new higher value for a property. But how is average real estate appreciation across the county calculated?

Each year every county is required to submit to the state data on recent sales that is used to calculate a common level ratio or CLR. The CLR is intended to represent the average price appreciation for a county since the base year of its current assessment values. CLRs for each county are calculated and published annually by Pennsylvania’s State Tax Equalization Board or STEB.

A common practice since the 2012 reassessment has been for municipalities and school districts to appeal the assessments of individual properties. If a property’s current market value has increased by more than what the CLR estimates have been the average price appreciation for the county, the appeals process can result in a higher assessment. So for many homeowners whose property values are being appealed, the CLR is key to whether their tax bills change, and by how much.

One of the lawsuits currently working its way through the legal system challenges the data and the process used to calculate Allegheny County’s CLR. Plaintiffs argue that the data on recent real estate transactions submitted by Allegheny County to the STEB significantly underestimates how much average home prices have increased since 2012. If true, new assessment values resulting from the appeals process are systematically higher than they should be.

However the ongoing lawsuit concludes, and no matter the accuracy of the CLR, the appeals process only impacts a relatively small fraction of roughly 580 thousand properties in the county. As of 2022, the vast majority of properties in Allegheny County continue to be assessed based on values set in 2012, and there is little to suggest any new mass reassessment will be conducted voluntarily by the county.

The situation in Allegheny County, like that in other Pennsylvania counties, persists because there exists no state mandate to do otherwise. Assessment procedures across the state remain highly decentralized. Unlike in nearby states where assessments recur on a set cycle by law, the potential of any mass reassessment is something of the third rail of local politics. There is nothing preventing Allegheny County from conducting a new reassessment or beginning a process to reassess on a regular schedule. But there appears no prospect Allegheny County will voluntarily begin any new reassessment effort, and no current litigation seems to be heading toward a repeat of a court-ordered reassessment as happened in 2000, 2001, and 2012.


The author consulted with attorneys for the Community Justice Project during the course of litigation over reassessments referenced here between 2000 and 2001.


Additional Bibliography

Robert Carbone and Reinhard S. Lai, “Assessment Of Urban Residential Properties: An Empirical Study of Pittsburgh,” J. Environ. Sys 4 No. 3 (Fall 1974): 207–216

Report of Committee to Study and Report on Assessment Practices, Procedures and Policies in Allegheny County, Prepared at the Request of the Board of County Commissioners, County of Allegheny, June 1976


[1] “Triennial Assessment Underway,” Pittsburgh Post-Gazette, January 18, 1944, 1.

[2] Charles C. Cook, “Computers in Local Property-Tax Administration,” Proceedings of the Academy of Political Science, 35 №1, The Property Tax and Local Finance (1983): 101.; also John O. Behrens, “The General Nature of the Property Tax Today,” 35 №1, The Property Tax and Local Finance (1983):14–30.

[3] Sam Spatter, “Judge Set to Rule on Assessments,” Pittsburgh Press, September 30, 1979, 93.

[4] The Longini-Carbone technique here is considered a variation on what is known as a Kalman filter which was used in ballistic trajectory estimation. See: Stuart I Bretschneider and Wilpen Gorr, “On the relationship of adaptive filtering forecasting models to simple brown smoothing,” Management Science, 27 no. 8 (August 1981):965–969.

[5] Robert Carbone and Richard L. Longini, “A Feedback Model for Automated Real Estate Assessment,” Management Science 24 No. 3 (1977):241–248.

[6] Sam Spatter, “Even break on assessments is team goal,” Pittsburgh Press, September 28, 1975; also Sam Spatter, “Judge Set to Rule on Assessments,” Pittsburgh Press, September 30, 1979, 93.

[7] Professor Longini also described this pushback from assessors in an interview with the Post-Gazette during the 1990s. See: David L. Michelmore, “Assessing the Hard Way,” Pittsburgh Post-Gazette, June 19, 1994.

[8] Ian James, “Appraiser waives off cries of conflict,” Tampa Bay Times, October 29, 1996.

[9] David L. Michelmore, “Assessing the Hard Way,” Pittsburgh Post-Gazette, June 19, 1994.

[10] Ron Schultz, “Research and Technology Update: The Other Market Model,” Assessment Journal (January/February 2001):48–50.

[11] CONSAD Research Corporation (Pittsburgh, PA), Improving the Reassessment Program, prepared for the County of Allegheny Office of Property Assessments, October 17, 2001. Page 7 addresses the exclusion of property values under $10,000.

[12] See Clifton v. Allegheny County,


None yet, but there will be.