I’ve found knowing the 1/e rule helps a lot with reducing stress when interviewing. It’s knowing that, if I haven’t randomly landed outside the first third, they should optimally say no to me, regardless of performance.
Brides.com says that most people date 1-3 years before proposing. Shortest I’ve ever broken up with someone is a few months so that should probably be shortened a bit. CDC.gov says the mean age or marriage is a touch under 30. If that is the first third, our dating age is about 20-50, which is probably a bit too wide if kids are on the table. So I’m going to say N is somewhere between 10-50, with the lower end of the range much more likely for.
Certainly it's not in the billions unless you spend an impressionable amount of time traveling. Realistically your personal total addressable market is certainly well less than 100k, probably less than 10k. You can subdivide further based on obvious preferences.