I hope it has not happened to 'most' women, and I've certainly, thankfully, never had anything really bad happen to me, but when I was being bullied at school, in 2 cases the way boys behaved towards me would be classed as sexual harassment if it happened between two adults (mainly trying to grab me or making inappropriate crude comments to me - and it happened on the school bus so I couldn't even get away from the situation).
It was very upsetting at the time (I was in the first year of senior school, so only 11/12) - the worst thing I remember was having to sit next to him when there were no other spare seats on the bus. I asked a friend to swap with me, which she did, but he then started hitting her and wouldn't stop unless I swapped back and went to sit next to him again. Hurting my friend to get at me - what a hideous, hateful thing to do. It's that memory that haunts me more than the sexual bullying.
As an adult, I've not experienced it very often, but was once groped in a bar by a man who was trying to chat me up. I was abroad on my own, so realised I was in a fairly vulnerable situation, but was able to make my excuses politely but firmly and leave.
I had to go and sit in a Starbucks and drink a cup of tea after as I was shaking and quite upset, but as an adult responsible for my own life & my choices, told myself chalk it down to experience, be grateful it wasn't worse and get on and enjoy the holiday. I was in New York by myself so I really didn't want to spend the rest of my time there feeling scared - but it did make me wise up to the fact that people who appear to be friendly & chatting to a tourist may actually be looking for something else. I hadn't realised the bar I was in was a 'notorious pick up joint' - as i later read in my Rough Guide.