During the 1990s, the United States and Russia -- a far poorer country emerging from totalitarian rule and beset by official corruption and organized crime -- vied for the dubious position of the highest incarceration rate on the planet.

But in the last few years, Russian authorities have carried out large-scale amnesties to ease overcrowding in disease-infested prisons, and the United States has emerged unchallenged into first place, at 702 prisoners per 100,000 population. Russia now has 665 prisoners per 100,000.

United States imprisons at a far greater rate than developed Western nations and many impoverished and authoritarian countries. On a per capita basis, according to the best available figures, the United States has three times more prisoners than Iran, four times more than Poland, five times more than Tanzania and seven times more than Germany.

A major cause is the war on drugs. In 1980, says Marc Mauer, assistant director of the Sentencing Project in Washington, about 40,000 Americans were locked up for drugs-only offenses. Now the number is 450,000, three-fourths of them black or Latino, though drug use is no higher in those groups than among whites.