There has been a 39 percent reduction in player arrests from last year.

The NFL, however, has had difficulty gaining cooperation during investigations into player misconduct.

The league formed a personal conduct committee last December.

"The committee is cognizant that, as a private employer, the league is taking on a challenge most other employers do not assume," the letter reads.

According to the report: "Between 2007 and 2014, the league averaged approximately 70 arrest incidents annually for players, 20 for violent and 50 for non-violent conduct. Since Jan. 1, 2015, there have been 11 arrests for violent offenses and 28 for nonviolent offenses, a 44 percent decrease in total arrests from the historic average, and a 39 percent decrease in total arrests as compared to the same period in 2014."