Voter turnout is a calculated statistical percentage of eligible, and in some cases registered, voters who vote in an election. In most cases, a high percentage of eligible voters participating in an election is desired, and most elections bring with them additional campaigns to increase voter turnout. The percentage of voters who cast a ballot in any given election is often used as an indication of the satisfaction of voters with the system of government in place in their country, although turnout tends to fluctuate over time. Voter requirements and restrictions, however, vary widely in different countries. Turnout is often indicative of this difference, especially in countries where voting privileges are either restricted or, at the other extreme, compulsory.
While the probability of a single vote having an effect in an election is rather low, the greater number of individuals who vote increases the possibility of wider demographic representation in the election. Historically, the number of eligible voters who participate in elections has varied widely based on any number of factors, whether economic, religious, or institutional. It is widely accepted that older populations tend to have a higher voter turnout than young populations. In some countries, especially the United States, marketing campaigns aimed at increasing the number of voters are generally directed toward those in younger age groups.
Partisan divisions along with overall distrust of the government, and consequently the electoral system, may also contribute to lower percentages of eligible voters turning out on election day. The additional requirement of previous registration to vote may also significantly decrease the overall number of voters. Countries and regions that automatically register eligible voters have shown an increase in voter turnout in comparison with areas that require the additional bureaucratic step of registration. Compulsory voting, practiced in some countries, has by nature resulted in a significantly higher voter turnout, although the varying degrees of penalization for failing to vote can limit its overall effectiveness.
In general, well-established democracies have displayed a general decrease in voter turnout since the 1960s. While these statistics have fluctuated over time, they are often considered the result of the governmental stability of the countries in question. As changes in elected officials are sometimes perceived as causing little to no change in the overall operation of the system, many potential voters are not inclined to cast ballots they view as ineffective.