Prop13 Subsidy Mapping Project

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(Redirected from Equity Mapping Project)
it's cookin' on Twittah

[names for this being debated:  Proposition 13 Subsidy Map, Proposition 13 Equity Mapping Project..?].

Suggested hashtag: #Prop13mapping.
Project Twitter account: @Equity_Map.


In the Bay Area and California, like other high-growth regions around the world, there have been dramatic rises in property values in recent decades. Additionally, in California, the Proposition 13 tax-limitation measure of 1978 means that there are sometimes large disparities in the effective tax rate paid by residential property owners vis a vis estimated property market values and a situation in which those owning for longer pay lower property taxes. 

Image Source:

[Image Source: California-Median-Home-Price-Map.png]

Equity Mapping Project  (provisional name) is a project to map and visualize 

  1. Housing property wealth gains
  2. Proposition 13 tax subsidies, i.e. disparities between taxable (assessed) and actual (estimated market) value

Geographic focus of the project: San Francisco, the Bay Area, and California (i.e. the jurisdictions affected by Proposition 13). 


originally suggested by Tim McCormick as "Anti-Dynastic Wealth Mapping Project" on Twitter, 2015 (?) (add cite). 


Tim McCormick‏ @tmccormick  21 Aug 2015
@kimmaicutler @antievictionmap or we could just raise the #transfertax on all property, make the donation non-voluntary. Few % = big tax $$$



See also,

 Thread 5 Sep 2016:  

Dave Guarino‏ @allafarce
Has anyone already done a property-level view of Prop 13 assessed/market values? Seems like data is there. @kimmaicutler @markasaurus

Kim-Mai Cutler‏  @kimmaicutler
Replying to @tbuck0 @allafarce @markasaurus
A regionwide map of the valuation differentials between assessments & market value would be fascinating.

31 May 2017

Name Ideas

note from a project member: 

"In general it would be ideal to have a name and general messaging that uses very simple, persuasive language to make it accessible to people who don't geek out on policy. In my mind, a big part of what makes this data so powerful is that once you surface it, you can trigger a strong, emotional response since it's immediately obvious to regular people how important and unfair it is, particularly because they can connect it to their own neighborhood and people they know. For example "Prop. 13 subsidies" - for almost everyone, the word "subsidy" triggers a basic sense of unfairness, particularly when it's not paired by something obviously important, like "subsidies to help poor people get health care" or whatnot."

compare: "Anti-Eviction Mapping Project".  References older organizations e.g Mission Anti-Displacement Coalition. 

Property Gains and Tax Subsidies Map

Data and Mapping Resources