What we found

FINDING 1

Cheaper homes are over-assessed, and it doesn’t have to be this way.

100% means the city’s value matches what homes really sell for. The cheapest fifth of Philadelphia homes is assessed at 124%. Those owners pay tax on more value than their homes have. The priciest fifth sits at 88%. Economists call this regressivity. In plain words, it quietly shifts tax off expensive homes and onto cheap ones.

The blue bars show the point: this pattern does not have to happen. Using only the city’s own open data, our model puts the same groups at 111% and 99% on the same sales. Most of the gap is gone. Regressive assessments are a modeling problem, and modeling problems can be fixed. See the proof.

Measured on mortgage-financed sales the model never trained on.

FINDING 2

Over a decade, that shifted roughly a third of a billion dollars.

Property tax is a fixed pie: every dollar the bottom over-pays, the top under-pays. Comparing each year’s roll to a fair one, lower-value homes over-paid about $357 million from 2016 to 2025 (about $226 per Philadelphian). $64 million of that came in the worst single year. On a stricter all-sales benchmark the total is closer to $650 million.

FINDING 3

Philadelphia has two housing markets.

About 4 in 10 Philadelphia home sales are all-cash. These are mostly investors and wholesalers, and they cluster in disinvested neighborhoods. Those homes sell for roughly 47% less than financed homes in the same district. In the cheapest fifth of recent sales, 6 in 10 are cash.

This part makes the story more complicated. Measured against regular mortgage-financed sales, the city’s fairness problem shrinks a lot. Much of the unfairness lives in the cash market, where homes are taxed on values they cannot actually fetch. Any real fix has to decide which market an assessment should reflect. We show both views.

FINDING 4 · IN THE CITY’S FAVOR

The same pattern shows up across the country.

• No number-gaming. We tested for “sales chasing,” which means quietly matching assessments to recent sales so official studies look good. Philadelphia comes back clean.
• Almost every city has this pattern. Research covering about 26 million U.S. sales finds the cheapest homes assessed at roughly twice the rate of the most expensive, nearly everywhere. Philadelphia isn’t uniquely bad. It sits inside a structural, nationwide failure. That is also why Finding 1 matters: the fix is a method other cities could use too.