The Obama administration on Friday announced a significant expansion of the FBI's definition of rape, which will now cover several forms of sexual assault and include male rape.

Justice Department officials said that the revision would make reporting of the crime more accurate and would provide a better understanding of its effects on victims.

Since 1929, rape has been defined as "the carnal knowledge of a female, forcibly and against her will." That definition, which included only men having sex with women without their consent, excluded other forms of sexual assault, such as oral penetration and rape of men.

The change is valid, IMHO, but there is one downside of changing a definition in statistical surveys that we need to be aware of.  Broadening the definition of a category of crime will cause an increase in the number of crimes reported in the category, even though there has been no actual increase in crimes committed.  Studies done on the data by researchers who are unaware of the change and fail to account for it can potentially mislead us.