Commissioner Roger Goodell and NFL owners put a toughened personal-conduct policy in place in December 2014. (Ross D. Franklin/Associated Press)

The number of NFL players arrested has declined significantly over the past year and a half, according to data compiled by the league.

The league’s data, obtained by The Washington Post, shows a 40-percent reduction in the number of players arrested between Jan. 1 and July 31 of this year compared to a similar period last year. That comes after a 38-percent drop in the number of players arrested for the entire year in 2015 compared to 2014.

“We’re pleased with the numbers,” said Anna Isaacson, the NFL’s senior vice president of social responsibility. “But it’s just one step. We’re not satisfied there. There’s more to be done. We’re looking at what more we can do.”

NFL owners unanimously ratified a revised personal-conduct policy for players and other employees in December 2014. The new policy included bolstered penalties for off-field misconduct and came after the league was sharply criticized by many observers in the summer and fall of 2014 for its handling of high-profile cases involving players such as Ray Rice, Adrian Peterson and Greg Hardy.

According to the league’s data, there were 21 arrests of players between Jan. 1 and July 31 of this year, six arrests for violent offenses and 15 arrests for non-violent offenses. That is down from 35 arrests between Jan. 1 and July 31 of 2015, 11 of those for violent offenses and 24 for non-violent offenses.

There were 42 arrests for all of 2015, 11 for violent offenses and 31 for non-violent offenses, according to the league’s data. That was down from 68 arrests in 2014, 20 of those for violent offenses.

There were four arrests this year through July 31 for incidents involving domestic violence and sexual assault. That was down from eight such arrests over a similar time period in 2015, six in 2014 and seven in 2013. Arrests for driving under the influence decreased to five this year from six last year, 13 in 2014 and 16 in 2013. There were no weapons-related arrests this year, according to the league’s data, after four such arrests through July 31 in 2015, one in 2014 and seven in 2013.

The decrease in the number of arrests illustrated by the league’s data appears consistent with figures compiled by independent sources. A database of arrests of NFL players compiled by USA Today lists 16 arrests through July 31 of this year, down from 31 last year through that date.

The tougher conduct policy approved in 2014 included increased penalties for cases of domestic violence: a six-game suspension without pay for a first offense and a lifetime ban, subject to review after a year, for a repeat offense.

Isaacson said she believes the education programs put in place over the past few years have affected the number of arrests, along with the deterrence provided by tougher penalties.

“I would think they’re each a factor,” she said in a phone interview. “There’s a tremendous amount of awareness now in the general public on these issues, and that’s a factor. I think it’s been really important. Our players speaking up on how they feel on these issues adds to the awareness in the general public.”

The sport is in its third year of social-responsibility education for players, coaches and staff members of teams and the league office. The education focused initially on domestic violence, sexual assault and child abuse, Isaacson said, but now includes additional issues, such as driving under the influence.

The league manages the education program in consultation with its outside advisers. There are sessions, roughly an hour long, for players and coaches performed annually on a team-by-team basis in training camps. Staff members receive their education and training during the season. The NFL’s rookie transition program for players, now likewise done on a team-by-team basis, includes a mandatory session on social responsibility. Individual teams have critical-response programs to deal with the issues of players and employees.

The NFL also has fostered relationships with other organizations, as when it announced in June that it had committed $10 million of funding to a collaborative initiative aimed at ending sexual violence.

The NFL Players Association had opposed the owners’ implementation of the revised personal conduct policy, saying that its terms should have been collectively bargained with the union.

The NFLPA filed a grievance last year related to the revamped policy. Arbitrator Jonathan Marks ruled in April that the league’s practice of placing players on paid leave via the commissioner’s exempt list with cases pending under the personal-conduct policy is valid. The union also has sought, unsuccessfully thus far, independent arbitration for players’ appeals of discipline imposed by the league under the personal-conduct policy and integrity-of-the-game rules.

The union did not immediately respond to a request for comment Wednesday on the reduction in player-arrest figures.

Isaacson said the players have been cooperative with the educational aspects of the league’s approach.

“On the education side, I feel the players have been very supportive of this,” she said. “It’s getting conversations started, and that’s important.”