Two houses in Berkeley side by side, one for rent
Similar houses on a block near the UC Berkeley campus may be paying different levels of property tax. Photo: Frances Dinkelspiel

Walk the leafy streets near UC Berkeley’s Clark Kerr campus and you’ll come across a three-bedroom, three-bathroom home whose value Redfin puts at $2.34 million. Its owners are paying $28,000 a year in property taxes.

Go farther on the same block and you’ll see another three-bathroom, three-bedroom home with a nearly identical Redfin value of $2.27 million. Its owners are paying about $6,000 in property taxes.

What the heck?

Welcome to the weird world of California homeownership, where the time when you bought a home influences how much property tax you pay (2017 in the first case, 1973 in the latter). Now, thanks to the brow sweat of data visualizer Ian Webster, you can explore the vast tax gulfs among homes in Berkeley and beyond — and if you’re a relatively new buyer, get mightily P.O.’d at how little many of your neighbors are paying.

Webster, a 30-year-old software engineer in San Mateo, scraped more than 5 million online records to create maps of property taxes in 12 California counties, including Alameda, Sonoma, Marin and Contra Costa. Parcels that pay the highest 10% of property tax in your browser viewport are marked in red, those paying the lowest 10% are green, and the middle 80%  are black. Click on individual properties to pull up government tax records, photos from Google Street View, and listings on Redfin and Zillow.

See Berkeley property taxes on a map

A flyby of Berkeley on Webster’s map reveals a dizzying quilt of property tax bills, from $15,000 tabs on modest-sized but pricey new purchases around San Pablo Park to grand old homes in the Berkeley Hills that are worth millions but dinged just a few thousand in property taxes a year. It’s not too difficult to find places with bills as much as 30 times greater than neighboring properties — a juxtaposition not quite as jarring as the 100-times disparities you’ll see in Palo Alto, but eye-opening nevertheless.

“I think the main surprising thing is you can zoom in to pretty much any block in the Bay Area and find examples that kind of make you scratch your head,” said Webster. “I don’t know what is right or wrong here, but just the fact there are these massive disparities suggests the policy is broken in some way.”

Locals will no doubt recognize this “policy” as Proposition 13, an initiative voters approved in 1978 that rejiggered the property-tax system across the state. (Voters at the upcoming election are being asked to modify Prop 13 with Proposition 15, which would allow commercial properties to be reassessed regularly and not just when they are sold.)

“There was a real concern [back then] which was that there were seniors living on fixed incomes who, in a period of really high inflation, were finding their houses were going up double, triple, quadruple-many-more times than what they paid for it. And the property taxes were going up with it,” said Jesse Rothstein, a professor of public policy and economics at UC Berkeley.

To help vulnerable populations deal with skyrocketing property taxes, Prop 13 froze everybody’s assessment basically at the amount they paid for the house, with only 2% annual increases in assessed values from thereon. That means your California property tax bill is basically what it would’ve been when you bought the house – people who live in their houses for 40 years are paying property taxes based on what their houses were worth 40 years ago.

Prop 13 pretty much guaranteed that nobody receives surprise property tax bills. But it also spawned complications in the housing market.

“It means people who are coming in later can pay multiples – their contributions are 10 or 30 times greater toward public services that we all rely on and use in our daily lives,” said Webster.

“There’s just a lot of inequity,” said Rothstein. “It makes it harder for people buying houses. And it encourages people to stay in their houses well beyond when that’s the right house for them, just because they don’t want to give up the low property-tax bill they’re paying.”

To judge from the online reaction, Webster’s map is achieving its intended goal of educating people about the effects of Prop 13. (The project is open-source; you can help expand it to all of California on Github or donate to bandwidth costs here.)

“WOW! This is an incredible tool! My neighbors are paying almost nothing!!!” one person wrote on Twitter. “I’m paying 58 x what one of my neighbors pays,” said another on the Bay Area Reddit. “My entire lot is 3,300 sq. ft. Theirs is over an acre. Similar size houses on each. Seems fair.”

Another Redditor has this simple advice: “If you bought any time in the last five years: Don’t click, it’s not worth it.”

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John Metcalfe is an Oakland-based freelance reporter who's written for Berkeleyside, The Washington Post, The New York Times and The Atlantic. He enjoys covering science, climate and weather, and urban...