Most of America’s prisons are in poor, rural, predominantly white, Republican-voting areas. The Census Bureau counts people as residents of the place they usually sleep, so prisoners count as residents of their prisons.
But the inmates themselves are more than 50% African-American or Latino. The Census Bureau rule artificially increases the nominal population of those areas (and thus their voting power and share of federal dollars) at the expense of the places the inmates actually come from and will return to. That helps stack legislatures with supporters of more and more incarceration: the repeal of the Rockefeller drug laws in New York was delayed for more than a decade by northern-tier state senators who feared the loss of prison-guard jobs for their actual constituents.
There’s a grim echo here of the “three-fifths rule” under which the voting power of slaveowners was inflated by counting a fraction of slaves as part of the population.
The effect is not a small one: the current prison headcount is 1.5 million. Is is really too late to change the rules before the 2010 Census?