We all know that the rich in the United States tend not to live in the same neighborhoods as the poor, but it is perhaps less well-known that such residential segregation is on the rise. We can quantify this increase in segregation by asking (a) how likely it is for households in the top fifth of the income distribution to live with households not in the top fifth (in 1960 and 2000), and (b) how likely it is for households in the bottom fifth of the income distribution to live with households not in the bottom fifth (again in 1960 and 2000).