Also regarding the connection between the “shidduch crisis” and girls’ going to school/starting careers, I have noticed the following: From the limited numbers of shidduch-age girls/boys that I know in the US, I have seen that many girls do not end up getting married until they are 2 or 3 years out of seminary, despite their best attempts to get married as soon as they are back from seminary, as they seem to think they are supposed to do.
I wonder if this is precisely because the boys only start shidduchim at around 23 so their “besherts” do not start shidduchim until 2-4 years after they do (since many girls end up marrying boys who are only 0-3 years older than them).
I have often thought, as WTP mentioned, that perhaps the “solution” to the “age-gap theory” is that the girls should start shidduchim later.
I think that the main reason for the “shidduch crisis’ is that people call it a “crisis” if a girl is not married by 20. It doesn’t have to be a crisis, and it wouldn’t be a crisis, if girls didn’t feel that they had to get married as soon as they get back from seminary.
It would probably put a lot less pressure on them if they didn’t feel that way.