Population Shifts in Congressional Redistricting

Population equality across congressional districts within a state is a hallmark of the redistricting decisions issued by the Supreme Court cases in the 1960s. Beginning with Wesberry v. Sanders (1964) and following from Karcher v. Daggett (1983), the norm has been to minimize differences in district total population after redistricting. Abolishing malapportionment has given rise to new forms of electoral manipulation. Courts, commissions, and legislatures may achieve population balance across districts in different ways. This article builds on a previous study that estimated the shift in population in the 2000 redistricting cycle by accounting for population shifts in the six redistricting cycles since the 1970 census. We find population shifts have more than tripled in this time. We show population shifts are a function of the size of the congressional delegation, whether seats are gained or lost in apportionment, the political match or mismatch between an incumbent’s party and the party in control of the redistricting process when the legislature draws the map. With an eye toward institutional variation in redistricting, we show appointed and independent commissions draw significantly different plans with regard to the preservation of previous districts. District change is high among partisan gerrymandered plans and plans drawn by independent commissions, though we find the latter are associated with changes in apportionment.