It's both. You have many factors that make numbers which is why I agree that the wage gap is less then what they are saying . But there is still a gap. As a female, I experience sexism. It may not be everyday, but there are times where I'm left like WTF.
So, to say that sexism doesn't play a role is nieve. It's in peoples minds. Frankly, theres a lot of men that do it and don't even realize that they are doing it because it's the norm. for example- I have friends that are guys and sometimes they make comments that are very sexist. like throws like a girl or cries like a girl comments. or how they have made the word cocksucker a derogatory term. I thought that was suppose to be a good thing?(its no wonder i dont ever want to do it.) what does that say about the people who do it? just saying...... I've brought it up once or twice and ask them what they thought. after bringing it up, they agreed I was right but it doesn't matter because they still do it. Lack of respect? No, I don't think so. it's more a habit I think. at least I hope they don't think less of me. maybe they do?