According to the search results, the percentage of women who have experienced sexual assault varies depending on the type of assault and the time frame considered. Here are some of the statistics found:

• One in five women in the United States has experienced completed or attempted rape during their lifetime, which is equivalent to 20% of women.
• About 14.8% of American women have experienced completed rape during their lifetime, and an additional 2.8% have experienced attempted rape.
• Females ages 16-19 are four times more likely than the general population to be victims of rape, attempted rape, or sexual assault.
• Over half of women and almost one in three men have experienced sexual violence involving physical contact during their lifetimes. One in four women and about one in 26 men have experienced completed or attempted rape.

It is important to note that sexual violence is notoriously difficult to measure, and there is no single source of data that provides a complete picture of the crime. Additionally, many cases of sexual assault go unreported, so the actual percentage of women who have experienced sexual assault may be higher than the reported statistics.