I think this is a good framework to start with. I'm going to keep thinking on it. I'm working on some essays on the fertility crash that I may or may not ever finish, but if I do, I'll probably reference this list.
But my immediate reaction is that while you covered the other bases pretty well, there are some major factors missing from your coupling/marriage list. I'll name a few other causes of the decline of marriage that come to mind:
-- Post-Sexual-Revolution loss of sexual incentive to marry - I.e., "Why buy the cow?" This speaks for itself, probably the biggest incentive to marry across time, especially but not exclusively for men, is that sexual access was generally gated behind it. While enforcement was always imperfect, there was still ex post facto enforcement in the form of the shotgun wedding.
-- Loss of the male provider role - This was a source of constant pressure for women to marry and stay married in the not-so-distant past but is mostly obsolete outside of maybe the top decile of male earners due to women's improved earnings power and the existence of social safety nets. I also think a large percentage of men aren't really adapted to being useful husbands and fathers if their primary contribution to the family is expected to be other-than-monetary. It might be the case that they're not *capable* of adapting to that role. So women don't want to settle for them, which is rational, given their incentives.
-- Cultural changes producing mismatched expectations - I understand this to be a big one in places like East Asia and I think in Southern/Eastern Europe. But honestly, I think it plays some role everywhere. Some people (mostly men) have a more traditional idea of what marriage should look like, while others (mostly women) have newer ideas. This isn't necessarily just about patriarchy or male headship -- there can also be mismatched expectations on practical matters, finances, etc. Relatedly many people, especially men, don't really understand the purpose of marriage, in an age when all traditions are questioned. "Why do we need to bring a formal government sanction into this relationship?" Basically, the accelerated pace of cultural change has made it harder for the median person to find people with whom he/she agrees enough on the very idea of marriage to actually form one.
-- Fear of (no-fault) divorce - This also ties in with my previous point. I think the question of "What's the point of marriage?" is reinforced by the idea that a marriage can be dissolved at any time, for any reason or no particular reason, and relative to the past the social costs of doing so are greatly reduced.
-- Declining attractiveness - This is more speculative, but at least in the US I think it's near-certain that the median young man and young woman are less attracted to each other than several decades ago due to obesity, declining physical strength and athleticism on the part of the average man, deteriorating social skills due to more time spent alone/online, less effort put into attire/physical appearance, and all-around less effort to project masculinity/femininity. [Side note: older people these days seem to age better, in part due to the end of cigarette smoking, but that's not relevant to fertility.]
Relative attractiveness surely matters more than absolute, but unfortunately people probably factor visual media into their sense of "relative", and we're more immersed in it than ever (a point you covered already).
I think this is a good framework to start with. I'm going to keep thinking on it. I'm working on some essays on the fertility crash that I may or may not ever finish, but if I do, I'll probably reference this list.
But my immediate reaction is that while you covered the other bases pretty well, there are some major factors missing from your coupling/marriage list. I'll name a few other causes of the decline of marriage that come to mind:
-- Post-Sexual-Revolution loss of sexual incentive to marry - I.e., "Why buy the cow?" This speaks for itself, probably the biggest incentive to marry across time, especially but not exclusively for men, is that sexual access was generally gated behind it. While enforcement was always imperfect, there was still ex post facto enforcement in the form of the shotgun wedding.
-- Loss of the male provider role - This was a source of constant pressure for women to marry and stay married in the not-so-distant past but is mostly obsolete outside of maybe the top decile of male earners due to women's improved earnings power and the existence of social safety nets. I also think a large percentage of men aren't really adapted to being useful husbands and fathers if their primary contribution to the family is expected to be other-than-monetary. It might be the case that they're not *capable* of adapting to that role. So women don't want to settle for them, which is rational, given their incentives.
-- Cultural changes producing mismatched expectations - I understand this to be a big one in places like East Asia and I think in Southern/Eastern Europe. But honestly, I think it plays some role everywhere. Some people (mostly men) have a more traditional idea of what marriage should look like, while others (mostly women) have newer ideas. This isn't necessarily just about patriarchy or male headship -- there can also be mismatched expectations on practical matters, finances, etc. Relatedly many people, especially men, don't really understand the purpose of marriage, in an age when all traditions are questioned. "Why do we need to bring a formal government sanction into this relationship?" Basically, the accelerated pace of cultural change has made it harder for the median person to find people with whom he/she agrees enough on the very idea of marriage to actually form one.
-- Fear of (no-fault) divorce - This also ties in with my previous point. I think the question of "What's the point of marriage?" is reinforced by the idea that a marriage can be dissolved at any time, for any reason or no particular reason, and relative to the past the social costs of doing so are greatly reduced.
-- Declining attractiveness - This is more speculative, but at least in the US I think it's near-certain that the median young man and young woman are less attracted to each other than several decades ago due to obesity, declining physical strength and athleticism on the part of the average man, deteriorating social skills due to more time spent alone/online, less effort put into attire/physical appearance, and all-around less effort to project masculinity/femininity. [Side note: older people these days seem to age better, in part due to the end of cigarette smoking, but that's not relevant to fertility.]
Relative attractiveness surely matters more than absolute, but unfortunately people probably factor visual media into their sense of "relative", and we're more immersed in it than ever (a point you covered already).