I'll take a stab. > https://i.imgur.com/b07CQKU.png https://i.imgur.com/b07CQKU.png Higher age at marriage means that people are more sure of what they want b

I'll take a stab. > https://i.imgur.com/b07CQKU.png https://i.imgur.com/b07CQKU.png Higher age at marriage means that people are more sure of what they want by the time they settle down, so are less likely to regret their choice of partner. > https://i.imgur.com/0rWEnNh.png https://i.imgur.com/0rWEnNh.png More premarital sex also means more are sure of sexual compatibility before marriage. That's a massive component of a healthy relationship that the no-sex-before-marriage crowd gets no data on before committing. > https://i.imgur.com/l9E3rVY.jpg https://i.imgur.com/l9E3rVY.jpg More women entering the workforce means that there's more equality on many parts of the relationship. Speaking anecdotally, my parents (dad was in tech working long hours, mom raised us and did housework) always accused the other of not doing enough, and a big factor of that is that the type of work they did was more or less incomparable. How do you measure the effort and stress of corporate life vs that of raising kids? There's also the resentment a non-working partner can have of being completely financially reliant on the other. In the other direction, resentment for being seen as only good for being a source of money. Both parents having roughly equivalent types of work, financial power, and relationship responsibilities probably facilitates better communication and empathy.