[NittanyLion]

If 10,000 people cast votes in a district that only has 9,000 registered voters, the problem is not with the 10,000 votes but with the 9,000 registered voters.

If we assume the problem is not purging the voter rolls, shouldn't this be just the opposite? There should be many people registered that won't vote, because they moved or died.

[Alberta's Child]

That's correct, except that people who move from one district to another may still show up as "registered" in their old district and "not registered" in the new one. Any district with a very high voter turnout is probably one that has more voters moving in than moving out or dying.