Obama also has been stingy with commutations, applications for early release by those still serving federal prison sentences.
Under Reagan and Clinton, applicants for commutations had a 1 in 100 chance of success. Under George W. Bush, that fell to a little less than 1 in 1,000. Under Obama, an applicant's chance is slightly less than 1 in 5,000.
He has commuted the sentence of one individual, a woman with terminal leukemia whose case was championed by Illinois Sen. Dick Durbin.
"This idea of 'tough on crime' took root around the time of Ronald Reagan and it is striking that President Obama is showing so much less mercy than Reagan," said Jeffrey Crouch, a political science professor at American University and the author of "The Presidential Pardon Power."
Matthew Lehrich, a spokesman for the Obama administration, said in a statement Thursday that the president took his power to grant clemency "very seriously."
"Each recommendation received from the Department of Justice is carefully reviewed and evaluated on the merits," Lehrich said.
To determine who receives clemency, Obama, like his predecessors, relies on recommendations from the Office of the Pardon Attorney, the arm of the Justice Department that reviews applications. The office — led by Pardon Attorney Ronald Rodgers, a former military judge and federal prosecutor — rarely dispenses endorsements, however.
Several administration officials who agreed to discuss pardons on the condition of anonymity said the president pardoned nearly every person recommended by Rodgers for approval in his first two years in office, but that such applicants were few and far between. While the number of applicants has increased in recent years, Obama — based on Rodgers' recommendations — is denying more people more swiftly than any of his recent predecessors, the data shows.
"I don't think he has been given the same opportunity, by this process, to look at these petitioners as his predecessors were," said Mark Osler, a law professor at St. Thomas University in Minneapolis who launched the country's first law clinic for commutations.
Currently, two government officials said, there are about a dozen positive recommendations and hundreds of negative ones waiting for the president to act on.
At least one commutation request is pending. The White House also has asked for a fresh review of the case of Clarence Aaron, who is serving a triple life-sentence, without parole, for his role in a drug conspiracy. ProPublica and The Washington Post published a story about Aaron's case in May.
Obama last granted pardons in November 2011, weeks before ProPublica and the Post published a series of stories that found that between 2001 and 2008, white applicants were nearly four times as likely to be pardoned as minorities. African American applicants fared the worst, almost never receiving the pardons office's recommendation. The Justice Department has commissioned an independent study to examine ProPublica's findings.