What is Tax base fragmentation?

In the United States, local governments provide services from schooling to public safety. Unlike local governments in most other countries, US local governments get limited transfers from federal and state governments, and function without an equalization scheme. This means that what services a locality can provide depend heavily on the base of taxable property wealth within its boundaries.

We measure tax base fragmentation—the extent to which local government boundaries create fiscal inequality between neighboring municipalities—using a dataset of more than 138 million property tax assessment records in 2019. The result is a portrait of stark fiscal inequality, even between neighboring jurisdictions: Newark, NJ, for example, has a tax base of $49,000 per capita, while Millburn, 5 miles away, has $477,000—almost ten times as many resources per capita.

The level of tax base fragmentation varies across the country, shaped by political geography and economic segregation. In metros like Detroit, MI, or Bridgeport, CT—as well as rural resort areas like Aspen, CO—it is profound. But in other parts of the country it is much lower, whether because of lower inequality or because legal jurisdictions are large enough to encompass both wealthy and poor neighborhoods.

You can read more about our methods and findings in the accompanying academic paper, learn to use the map on the how-to page, or download the data by municipality and metro area here.