The number of illegal immigrants attempting to unlawfully reenter the United States rose 28-fold from 1992 to 2012, the Wall Street Journal reports.
The analysis was released by the Pew Research Center.
In 2012, unlawful re-entry cases accounted for 26% of sentenced federal offenders, second only to drug offenses at 32%. That is a 13-fold increase since 1992, when people sentenced for unlawful re-entry constituted just 2% of the total.
"Immigration has become a huge share of the federal docket," said Mark Lopez, the report's author.
People convicted of unlawful re-entry have entered or tried to enter the U.S. illegally more than once, or tried to re-enter after a previous deportation. For decades, people apprehended by the U.S. Border Patrol after trying to enter illegally were released in Mexico or ordered to appear in immigration court for civil proceedings. The Bush administration initiated a policy that made illegal re-entry a crime punishable by imprisonment to discourage people from sneaking in again. The average incarceration is two years.
The policy, known as Operation Streamline, has continued during the Obama administration. Those who back a stringent policy on immigration applaud the policy, which they say has contributed to the recent decline in illegal immigration.