No one can agree on a definition for rape, and so no one knows how often it's happening

Sexual assault is an all-too-frequent occurrence in the United States, but according to a new report by the Government Accountability Office, the federal government doesn't know just how often it happens. 

The Department of Health and Human Services, the Department of Defense, the Department of Justice and the Department of Education all investigate the rate at which sex crimes occur, but because they all have different criteria for measuring and categorizing them, they wind up with very different numbers — and without consistency, neither lawmakers nor laypeople can know what, exactly, we're dealing with. 

"As we continue to make progress in combating sexual assault and empowering survivors to come out of the shadows, we've got to have a way to measure that progress that's standard and transparent," Missouri Sen. Claire McCaskill said in a press release.

The GAO launched its investigation to determine what kinds of efforts the government makes to gauge sex crime rates, and to examine any variation in the way the offices understand and define different acts. The report found that the four departments run a total of at least 10 initiatives to collect data on sexual assault, and between them, they use 23 total terms to categorize various violent sex acts. What qualifies as rape for one agency might be "assault-sexual" for another, the report said. Each department has its own uses for the data and motivations for collecting it, and the way they define various offenses speaks to those. 

On top of these discrepancies in definitions, the departments don't make clear to the public how they measure one act against another. For lay readers trying to interpret the numbers, it can be tough to know what you're really looking at.

A huge discrepancy in reported sex crimes: The government offices that collect data on sexual assault report numbers that vary wildly. The report states that, in 2011 — the most recent year for which data is available — the rough numbers fell between 244,190 instances of rape and sexual assault by one department's count, and over 1.9 million rape and attempted rape victims by another's.  

"Without the ability to make apples-to-apples comparisons across populations — whether that's college students, our military or other groups — it's difficult to measure trends over time and determine how we're doing in terms of reducing incidents and boosting reporting," McCaskill said in her statement. 

"These agencies have to share their collection information publicly and talk to each other to develop real standards, and I look forward to working with them to ensure that happens."

The GAO is recommending that the Office of Management and Budgets convene a forum for the departments to do just that, allowing them to align their individual definitions of sexual violence for more cohesive data. The GAO also suggested that, accompanying their data, the agencies also release information on how they measure sexual violence, thereby helping readers to make sense of the numbers. 

One thing seems clear: The grand total of rape and sexual assault cases that occur annually is bound to be larger than what the government reports, even if its agencies can agree on definitions. By the Rape, Abuse & Incest National Network's count, two out of three rapes go unreported. However we measure it, sexual violence in this country is at crisis level.