Interactive Map Compares Californians’ Property Taxes

(TNS) — It's no secret that Proposition 13 has created huge disparities in property taxes in California, but seeing it all laid out on a map is an eye-opener.

Ian Webster, a 30-year-old computer scientist, has created an interactive map where people can look up almost any address in 16 California counties including the entire Bay Area, and see the tax on that property and all surrounding ones. It's not unusual to see one homeowner paying 10 or 20 times what a neighbor is paying, largely because they bought decades apart.

Totally at random, I picked 23rd Avenue between Pacheco and Ortega in San Francisco's Sunset District, where homes tend to be of the same size and vintage. The tax on one house, which sold in 2015, is $21,400 a year. Four doors down, the tax is about $1,400 a year. Both are roughly 1,900 square feet and built in 1941. Zillow estimates their market values between $1.6 million and $1.7 million.

It's easy to spot disparities because the highest-taxed properties in a neighborhood appear in red, the lowest in green, and all others are in black. Clicking on a home takes you to the county tax record for that address.

Webster, a Dartmouth computer science grad, works for software company Zenysis, which uses public health data for purposes such as tracking the spread of infectious diseases in developing countries. But he created the property tax map on his own time.

With the election coming up, he had been hearing a lot about Prop. 15, which if passed would make the biggest change to property taxes since Prop. 13 passed in 1978.

Under Prop. 13, real estate in California generally is reassessed at market value when it is sold or transferred. (Some transfers are exempt from reassessment.) In between changes of ownership, the assessed value can go up by no more than 2% a year, plus the value of improvements. Property taxes average about 1.2% of assessed value. Normally, when properties turn over after a long period of time, the tax goes up because market values have usually risen more than 2% annually.

Prop. 15 would require most commercial properties (but not residential ones) to be reassessed at least every three years. Separately, Proposition 19 would change some exemptions to reassessment; it would expand those for older adults and people with disabilities but rein in those for transfers between parents and children.

"I heard a lot of different arguments about Prop. 15. Usually my reaction is, I want to look at the data," Webster said.

Although it's fairly easy to look up a home's property tax on real estate websites such as Zillow or Redfin, or on a county tax collector's website, Webster knew of no free sites that mapped it out for large parts of the state.

"This data, although it's ostensibly public, ought to be put into a form that people can use to analyze" the pros and cons of Prop. 13, Webster said.

Creating the program was "a fairly arduous, tedious process. We have to build something that can access each of these tax websites," Webster said. "I found (geographic information system) data files for all the parcels within a county. I take that data and feed that into a program which goes and looks up taxes for each of these properties."

He started with San Francisco, San Mateo and Santa Clara counties and was "so blown away by the response" he added more. "I have open-sourced this project; others have contributed their own counties," he added. In addition to the Bay Area, it includes Los Angeles, Sacramento, San Bernardino, San Diego, San Luis Obispo, Santa Cruz and Yolo counties, which together include more than half the state's population. More counties are coming soon.

Webster said the site has had about 50,000 unique visitors since it launched a couple of weeks ago. It's gotten a lot of attention on social media such as Twitter and Reddit.

When he adds a county, Webster spot-checks it for accuracy. He's had some irregularities on recently sold homes in Marin County, with supplemental taxes for a partial year showing up instead of the full year's tax. When a property is sold, the supplemental tax bill represents the tax due on the difference between the old and new assessments for months remaining in the fiscal year.

That's why there's a warning on Marin County homes that says, "Due to a scraping issue, Marin properties sold within the last year are displaying incorrectly with low tax. This issue affects a very small number of properties. Please check the tax records before sharing."

Although Prop. 15 got him thinking about this, Webster said, "When I published this site, I wanted to be careful about not editorializing. I have my own view on the propositions and taxation, but it's really important to me that people have factual data based on public information. The data speaks for itself."

To see the map, go to www.officialdata.org/ca-property-tax.

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