Sexual assault data -- what gives?

Can it be that reported sexual assaults are up but prosecutions down? So it seems, according to the Defense Department's FY17 report. Dan Lamothe writes here in the Washington Post. Excerpt:

[T]he percentage of cases that the U.S. military prosecuted criminally declined. In fiscal 2013, the Pentagon reported that 71 percent of cases resulted in criminal charges being referred to courts-martial. That number fell to 64 percent in fiscal 2014 and 2015, dropped to 59 percent in 2016 and declined to 54 percent last year.

Nate Galbreath, deputy director of the Pentagon’s Office for the Prevention of Sexual Abuse and Response, said Monday that there is “no right number” when it comes to sexual assault prosecutions. The Pentagon setting one, he said, would raise the possibility of unlawful command influence, a legal term in military justice in which senior officials compromise the fair prosecution of cases by getting involved.

He's right: settling on a "right" number would indeed make unlawful command influence lights and buzzers go off. Two possible explanations for the apparent decline in prosecutions come to mind. First, perhaps the in terrorem effect of past Senate actions against selected convening authorities who took the "any reason or no reason" clause of the Manual for Courts-Martial literally -- think "unlawful congressional influence" -- has burned off with the passage of time. Second, perhaps convening authorities, staff judge advocates and chiefs of justice have noticed an uptick in the rate of acquittals -- suggesting that non-meritorious cases were being uncritically referred for trial.

Comments are invited (real names only, please).

Postscripts. (1) There's a third explanation, according to this piece by Jeff Schogol in Task & Purpose: more sexual assault cases are being disposed of through administrative action (meaning nonjudicial punishment) and administrative separation. See Fig. Q from App. C, p. 28.

(2) According to another chart in Appendix C to the FY17 report (Fig. J, at p. 16), 14% of victims of sexual assault declined to participate in the military justice process. With the exception of FY10, when the declination rate was 17%, the FY17 rate was the highest in the last nine years.

(3) The FY17 court-martial acquittal rate in "penetrating crimes" was 34%. It was 22% in other ("sexual contact") sexual assaults. See Fig. S, at p. 30. The chart does not provide longitudinal data for acquittal rates.