Collocations for turnout - noun

good, heavy (esp. AmE), high, huge, massive, strong
record
a record turnout for an election

low, poor
40%, 70%, etc.
electoral, voter
Voter turnout was high at the last election.

depress, suppress (both AmE)
That could depress turnout in a few states.

boost, increase

a decline in turnout, a fall in turnout, an increase in turnout

big, fantastic, good, great, impressive, large
disappointing, poor

attract (esp. BrE)
The concert attracted a large turnout.

get, have
I think we will have the biggest turnout we've had for quite some time.