The total number of sexual-assault reports at the three U.S. military academies increased slightly last year, but an anonymous survey suggests far more encounters are going unreported, according to a new report by the Department of Defense. The survey says the number of students at the Army, Navy, and Air Force academies saying they experienced unwanted sexual contact increased by nearly 50 percent over the 2016 survey. More than half of the encounters involved alcohol, and the survey found nearly a third of male students and 15 percent of females said they drink heavily. The 2018 survey, which is conducted every two years, was the first time participants were asked about alcohol use. Defense officials said Thursday they are frustrated and disheartened by the results. “Our cadets and midshipmen must be role models if they’re to lead the world’s finest fighting force,” said James Stewart, performing the duties of undersecretary of Defense for Personnel and Readiness. “This year’s report demonstrates that there is more work to be done to meet this goal.”