Coercion means drugs, alcohol (the #1 date rape drug and impossible to give consent when under the influence), threats of violence, physical force, mental coercion, blackmail etc.
When we label an assault as sexual assault we are separating it from general physical assault. So we are talking about everything from rape to inappropriate touching.
The stat is not ridiculous. It is a life burden for your mom, wife, sister, daughter and grandmother because raping the elderly and the bedridden is its own unique cohort in this discussion.
When we use 1/3 we mean that literally one in three women as based on current reports and surveys in sexual assault and rape crisis centers. When we say that these crimes are often unreported that means that the actual stat of sexual assault is in reality significantly higher. There is a lot of difficulty in naming accurate stats due to the incredible variance in communities and ages, whether or not it went to the police, age of victim, relationship to perpetrator (most rapists are either friends family or partners) etc. However, for the last twenty years that I have worked with the sexual assault and rape crisis center I have seen the generally accepted stat move from 1 in 4 to 1 in 3 and that's a globally accepted stat that most peope have difficulty in believing. However, if you listen to women, then they may share this reality with you. I'm saddened incredibly by the great number of women who have shared their story with me. The more you work on this subject matter the more stories you hear.
From wikiP: According to the American Medical Association (1995), sexual violence, and rape in particular, is considered the most under-reported violent crime.[9][10]
The most common reasons given by victims for not reporting rapes are the belief that it is a personal or private matter, and that they fear reprisal from the assailant. A 2007 British government report says "Estimates from research suggest that between 75 and 95 percent of rape crimes are never reported to the police."[11]
So you can figure things out from there. These are not meaningless numbers. This is what defines our society, our human relationships, our families and the sexual dynamics of the populous. It's not something made up. It has lifelong consequences and implications for us all.