When the Census Bureau counts prisoners, they are tallied at their prison addresses because that is their usual residence under census rules. Some government officials and advocates have urged the Census Bureau to count prisoners at their home addresses, arguing that counting them in prisons gives disproportionate power to the areas (often rural) where those facilities are located. This week, the Census Bureau agreed to give states more power to address this issue themselves when 2010 Census numbers come out.

Census population totals are used to draw the boundaries of state legislative districts or other voting districts, which by law must be of equal size. To illustrate the outsize power that some prison communities have, one advocacy group cites the example of Anamosa, Iowa, where counting the non-voting inmates in a prison gave the 56 people living in the ward where it was located effectively as much influence as the 1,374 people living in each of the other wards. The city later abolished the prison district. An evaluation of census residence rules in 2006 by the National Research Council (part of the National Academy of Sciences) said the evidence is “compelling” that political inequities result from current practice.

Bureau officials say it is impractical to count prisoners at their home addresses for a variety of reasons. For example, would a prisoner serving a life sentence be counted in a community in which he has not lived for decades? The National Research Council report agreed that currently it is not practical to do that, but said that improved record-keeping and census-taking procedures might make it possible.

Short of that, the council urged the bureau to provide detailed counts of prison populations at the census tract or block level more quickly, so as to help states and localities decide on their own whether to exclude inmates in drawing up boundaries of legislative and other voting districts. The Census Bureau by law must provide block-level basic population data by April 1, 2011 to help states with their redistricting process. Under the usual timetable, the detailed data about prisoners might not be available until summer of 2011. According to advocacy organizations and news accounts, the bureau has committed to produce the detailed data by May 2011.