The 'Race Ratio' is the percent of people of a race within X miles of the facility (or point) divided by the national median (Census 2010). If the ratio is greater than 1 that means that people of that race are disportionately located within X miles of that type of facility (or point). The national averages (2010 Census) are 0.9497% American Indian, 4.753% Asian, 12.61% Black, 16.35% Hispanic, 2.918% Multi-Racial, and 63.75% White (this exceeds 100% due to how the Census counts Hispanics).

The Income Ratio is the weighted average of median household income (ACS 2010-2014 5 year average) of people within x miles of the facility (or point) divided by the national median ($52,762). If the ratio is lower than 1, that means that low-income people are disproportionately located within X miles of that facility (or point).

Geographical units for Race: Blocks up to 5 miles, block groups up to 50 miles, then census tracts.
Geographical unit for Income: census tract

Note: for the larger distances the total population will exceed that of the US as people who live near multiple facilities (or points) are counted once for each facility (or point).

The Population Sample is all of the people in that radius that have race or income data. The population sample for income data can differ significantly from that of race, especially at small radiuses (1 mile and less) due to income requiring a larger geographical unit of analysis. Also, the income population sample size may include as few as one census tract. You can estimate the number of census tracts by dividing the income population sample by 4000. Any income population sample size that only includes several census tracts is subject to a large confidence interval.

User Notes
http://feeds.bayareabikeshare.com/stations/stations.json

Technical Notes

Execution time: 4 seconds

Credits: JusticeMap.org, Energy Justice Communities Map, Census Bureau (2010 Census and 2010-2014 American Community Survey).

Email me

	Distance (in miles)
	0.1	0.25	0.5	1	2.5	5	10	25
American Indian	0.65	0.66	0.7	0.7	0.7	0.68	0.6	0.61
Asian	34.22	38.61	36.07	35.39	27.28	25.1	32.73	28.04
Black	7.13	6.64	6.63	6.36	5.66	5.22	6	7.39
Hispanic	11.95	12.9	14.83	16.13	19.74	22.62	20.9	22.45
Multi-Racial	3.73	4.02	4.15	4.28	4.56	4.8	4.89	5.26
White	42.88	38.38	38.99	38.7	43.86	43.57	36.79	38.11
Population Sample	19k	138k	569k	2,430k	11,403k	27,989k	66,456k	170,392k
Density	170,392k	170,392k	170,392k	170,392k	170,392k	170,392k	170,392k	170,392k

Income	$52k	$52k	$60k	$59k	$72k	$82k	$85k	$88k
Population Sample	6,992	149k	566k	2,429k	11,305k	27,806k	66,334k	170,602k