Using address information from the NYC Board of Elections voter rolls, WNYC determined how many people voted in 2009 municipal elections (primary, runoff and general) in each census tract. We then compared that number to the estimated number of adult citizens in each tract, according to the US Census 2011 5-Year American Community Survey. Our data and more details.

Felons, who cannot vote, are not considered in the calculations for this map. Also, because NYC address information and official census tract demarcations can be imprecise in spots, voters who live on some tract borders may be counted in a neighboring tract instead.