This map compares voter residency requirements today across the states. In general, there is relatively little variation compared with the past. The 1970 Voting Rights Act imposed a thirty day maximum residency requirement in presidential elections. The U.S. Supreme Court in a 1972 decision extended this thirty day maximum to state and local elections. Nonetheless states do vary in what they expect of citizens. Fourteen states including Texas require a full thirty days residency. In practice this means that a voter may not vote until thirty days after registering to vote. Twenty-one states require residency between twenty and twenty-nine days. Nine require residency of one to nineteen days. Finally, seven states either through a form of "instant" registration or the absence of any registration requirement at all reduce the residency requirement in effect to presence in the state on election day. Longer residency requirements--in the past sometimes as long as two years--were justified as a form of fraud prevention or as a way to ensure a voter's close connection with, investment in, and knowledge of his or her community. In practice, longer requirements simply disenfranchised the more mobile segments of the population, doing little to reduce fraud or increase voter knowledge.