America has long been the country with the highest rates of incarceration in the world, yet it has never been one of the safest nations. A new research report released by the Brennan Center finds not only that incarceration has had a negligible effect on the overall crime rate, but that incarceration has continued to increase even as crime rates dropped.  

“Since approximately 1990, the effectiveness of increased incarceration on bringing down crime has been essentially zero,” report authors Oliver Roeder, Lauren-Brooke Eisen and Julia Bowling wrote earlier this month.

No country in the world imprisons more of its citizens than the United States. While it is home to just 5 percent of the world’s population, it is also home to 25 percent of its prisoners. That overall share grew dramatically at the close of the 20th century, when the size of the U.S. prison population more than quintupled after 1970. According to research conducted by the Center on Policy and Budget Priorities, the prison population has more than tripled as a share of the general population in 36 U.S. states. 

This increased emphasis on incarceration began amid the tumult of the 1960s, and for years, its merits and effects have been the subject of debate. In November, the Federal Bureau of Investigation announced that the U.S. crime rate had dropped to its lowest level since 1978, and while high rates of incarceration were listed among the factors contributing to the decline, it was just one item on a long list that also included things like the increased age of the U.S. population, lower levels of unemployment, increased video surveillance and improved police tactics. The Brennan Report found that high incarceration rates had just a 6 percent effect on the drop in crime rates.

Separate research released in November found that in states where incarceration rates fell, overall crime rates dropped as well. Over a five-year period when California’s incarceration rate dropped 15 percent, the state’s crime rate declined 11 percent, according to research conducted by the Pew Research Center.