>The base population Gans uses includes a growing population of
>unnaturalized immigrants and felons who can't legally cast ballots.
The Census Bureau uses the entire adult pop, not just those eligible to vote, as its denominator in turnout. The rationale: even noncitizens and felons have to pay taxes and obey the law. I got into a big fight with the editor of my State of the USA Atlas on this issue back in 1994; with the Census person on my side, I won.
Doug