Massey and Denton argue that low levels of segregation in towns with very small black populations is the product of open (nondiscriminatory) housing markets, which are tolerated in such towns because the probability of a white person having contact with a black person is extremely low in any event (American Apartheid, 111-112). Segregation, of course, is not the only indicator of the presence of racial discrimination. Idaho has little racial segregation, but it is the only state outside of the South that is subject to preclearance requirements under the Voting Rights Act. That is, because of its history of racial discrimination in voting, it must submit all proposed changes in its election practices to the Federal Government for prior approval before adopting them.