[maxerickson]

Matches up with my expectations (very low rates regionally here). Is the underlying source data publicly available?

Also, note that the OpenCycleMap tiles you are using request specific attribution: http://www.thunderforest.com/terms/

[davito88]

Yes. The data is from the US Census Bureau's American Community Survey: http://www.census.gov/data/developers/data-sets/acs-5year.ht...

Here is the script to generate the GeoJSON file: https://github.com/davidbailey/py/blob/master/walkbike2015.p...

Thanks for the info about attribution. I've updated the page.