Deputy Attorney General Sally Yates at the Justice Department last year. On Monday, Yates released data that shows federal prosecutors are pursuing fewer drug cases. (Evelyn Hockstein/For The Washington Post)

Federal prosecutors are pursuing fewer drug cases and filing charges that trigger mandatory minimum sentences less frequently — two indications, Justice Department officials say, that former attorney general Eric Holder’s initiative to reduce the prison population and enforce drug laws more judiciously has been a success.

The feds brought 6 percent fewer drug cases in fiscal year 2015 than they did in 2014, continuing a steady decline since Holder announced his “Smart on Crime” initiative three years ago, according to Justice Department data released Monday.

In 53.1 percent of the 2015 cases, no mandatory minimum sentence was triggered — compared with 48.7 percent in 2014 and 38.5 percent in 2013.

“We’re really happy with the direction,” Deputy Attorney General Sally Yates said at a briefing to announce the data. “We see it trending the direction we wanted it to see.”

Holder’s initiative, announced in August 2013, asked federal prosecutors not to bring charges that would trigger mandatory minimum sentences against low-level drug offenders and to consider whether cases were serious enough to warrant prosecution at the federal level. Yates said the idea was to ensure that Justice Department’s limited resources were being used efficiently, and that federal prosecutors were not unnecessarily filling federal prisons.

The initiative is not without controversy. Some federal prosecutors and local district attorneys nationwide have said that tough sentencing policies help law enforcement break up drug networks by putting pressure on lower-level defendants to plead guilty and cooperate and that long prison terms help bring down crime overall.

Yates said that data showed drug defendants have been pleading guilty at roughly the same rate since Holder’s initiative started, and she disagreed with the idea that it played a role in upticks in crime in certain parts of the country. She said the data showed federal prosecutors were focusing on the most serious drug cases, noting that the percentage of drug defendants with a weapon rose from 16.4 percent in fiscal year 2014 to 17.3 percent in fiscal year 2015.

The percentage of defendants who qualified for the so-called safety valve — reserved for non-violent offenders with little to no criminal history — fell from 37 percent in 2011 to 32 percent in 2015, the Justice Department said.