Thus , turnout has to be calculated based on population estimates .
In the United States , for example , there is no accurate registry of exactly who is eligible to vote , since only about 70 -- 75 % of people choose to register themselves .
Turnout has to be calculated based on population estimates .
In the United States , for example , there is no accurate registry of exactly who is eligible to vote , since only about 70 -- 75 % of people choose to register themselves .