The proportion of the registered electorate who vote in a given election. Turnout is both important and difficult to measure where registration is itself a costly process, especially in the United States. At the other extreme, regimes with compulsory voting (such as Australia), still have turnout well below 100 per cent, as the compulsory‐voting laws are rarely enforced. There has been a general tendency in a number of countries including the United Kingdom for turnout to decline since a peak in the 1950s. Some view this with alarm, others do not, either because too high a turnout has been argued to place too great a strain of conflicting demands on the political system, or because rational economic men and women who know that their own vote is highly unlikely to influence the election do not bother to vote. Some weak confirmation of the last view is provided by the association between turnout and the expected closeness of the election; but this explanation cannot explain turnouts of over 70 per cent in elections which nobody expected to be close, such as the British General Election of 1983. The collapse of turnout in that of 2001, when party policies were similar and everyone expected Labour to win, is, however, rationally explicable in this way.