The United States has the highest documented incarceration rate, and total documented prison population in the world. As of year-end 2007, a record 7.2 million people were behind bars, on probation or on parole. Of the total, 2.3 million were incarcerated. More than 1 in 100 American adults were incarcerated at the start of 2008. The People's Republic of China ranks second with 1.5 million, while having four times the population, thus having only about 18% of the US incarceration rate.