This map shows the change in the number of electoral votes for each state between the 2000 and 2004 elections. The electoral votes in the 2000 election were based on the 1990 Census, while the elections of 2004 and 2008 are based on the 2000 Census. With each census, if a state gains or loses enough population, it can also gain or lose congressional seats. Since each state's electoral votes are equal to its number of congressional and senate seats, a shifting population can affect the number of electoral votes each state has. So while the total number of electoral votes for the country remains the same (538), the number of votes each state has can change. Between the censuses of 1990 and 2000, there was a shift in population that led to more electoral votes in western and southern states while northern states lost electoral votes. Eighteen states either lost or gained votes between the two censuses.

The shift in population might seem to be favorable to a Republican candidate, since most of the states that have picked up votes are in the south, which have recently been red states. But it is difficult to tell whether the people who have moved into those states will vote more Republican or Democratic, as many of these migrants have come from northern, blue states or are Latino immigrants from Mexico and other parts of Latin America. You can click on states to access population data from the US Census Bureau.