Washington (CNN) The percentage of military personnel who said they were victims of sexual assault dropped dramatically over the past two years, plunging by about 27%, the Pentagon said Friday.

But only roughly a third of those victims reported specific incidents to authorities, and officials concede that the percentage of victims who say they have experienced retaliation for reporting sex crimes has not significantly changed.

The study, which was conducted by the RAND corporation and sponsored by the Pentagon, indicated that an estimated 18,900 soldiers, sailors, Marines and Air Force personnel said they were victims of "unwanted sexual contact" in the 2014 fiscal year, compared to about 26,000 in 2012. In the surveys, the Pentagon uses the words "unwanted sexual contact" as an umbrella term covering any sexual offense, from inappropriate touching to rape.

Pentagon officials said that, even as the number of victims declined, more people were willing to report that they had been victimized. According to the report, the Pentagon received 6,131 reports of sexual assault in the 2014 fiscal year, an 11% increase from the year before and a 70% jump from the number of reports that were made in the 2012 fiscal year. Officials say the increase in reports of sexual abuse suggests rising confidence among personnel that their complaints would be taken seriously.

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The decline in the number of people telling researchers that they had been sexually assaulted, which reverses years when they were rising steadily, is attributed to initiatives the military has undertaken prompted in large measure by congressional action.

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