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WASHINGTON (AP) — Reports of military sexual assaults jumped by 13% last year, but an anonymous survey of service members released Thursday suggests the problem is vastly larger.

The survey results found that more than 20,000 service members said they experienced some type of sexual assault, but only a third of those filed a formal report.

The survey number is about 37% higher than two years ago, when one was last done, fueling frustration within the department and outrage on Capitol Hill.

“I am tired of the statement I get over and over from the chain of command: ‘We got this, madam, we got this.’ You don’t have it!” Sen. Kirsten Gillibrand, a New York Democrat, shouted during a Senate Armed Services Committee confirmation hearing Thursday for Army Gen. James McConville. “You’re failing us.”

McConville has been nominated to be the next chief of staff of the Army, and that service saw a spike of more than 18% in the number of sexual assault reports filed last year. The Marine Corps had the largest jump, at 23%, while the Navy saw a 7% increase and the Air Force was up by about 4%

The Pentagon releases a report every year on the number of sexual assaults reported by troops. But because sexual assault is a highly underreported crime, the department sends out an anonymous survey every two years to get a clearer picture of the problem.

The increase in assaults has triggered another round of new Pentagon programs and initiatives to try to reduce misconduct.

Nate Galbreath, deputy director of the Pentagon’s Sexual Assault Prevention and Response Office, told reporters Thursday that the latest numbers are “disheartening and it personally makes me angry,” but he said he’s “not without hope.”

The survey found that young and junior enlisted women between 17 and 20 were most likely to experience sexual assault. In the vast majority of the cases the alleged perpetrator was a military man, often near the same rank as the victim and usually someone she knows. The report also found that nearly two-thirds of all incidents involved alcohol use by the victim and/or the offender.

Galbreath said the department has to reassess why prevention programs are not working as well with younger troops and adjust those efforts to better reach them. Programs that worked a few years ago, he said, are no longer effective.

The studies also found that there are often more problems in military units that have poor command climates or low levels of unit cohesion.

Last year, when the Pentagon announced that assaults in 2017 had increased by 10% over 2016, then-Defense Secretary Jim Mattis called the problem a cancer in the ranks and ordered the Department to re-double its efforts to prevent and respond to sexual assaults across the military. On Thursday, Acting Defense Secretary Patrick Shanahan called this year’s increase unacceptable and directed the military to enact new programs to identify serial offenders and beef up scrutiny of new recruits to ensure they have the right character for military service.

“Sexual assault and sexual harassment are persistent challenges,” Shanahan said in a memo to military service leaders. “We cannot shrink from facing the challenge head on. We must, and will, do better.”

Galbreath said one change expected to begin later this summer will have the military begin comparing information on offenders from victims who file so-called “restricted” reports. Filing a restricted report allows victims to seek treatment but they avoid any criminal complaint or prosecution. Many victims choose that route to skirt any potential retribution or stigma of a public trial.

Under the new plan, Galbreath said the military would put information on alleged attackers into a database so repeat offenders can be identified. Galbreath said if officials find a possible repeat offender, they would go back to the victims to see if they might change their minds and agree to prosecute.

According to the survey, 21% of the women who said they reported a sexual assault believed that they suffered some type of retaliation aimed at stopping them from making a complaint.

Separately, 133 service members filed retaliation complaints. Of those, two-thirds were investigated by department inspectors general and ultimately 13 received some type of punishment, ranging from counseling to a court-martial.