Let's start simple and say that the average person isn't bisexual, so we need to exclude half of people from the get-go. But maybe you're taking that as a given. So then we also need to consider that less than half the population is within your optimal age range. Maybe you're also taking that as a given. (But note that at this point we're already excluding 85% of humans.) Now consider that you also probably want them to speak your language. Again, maybe another gimme, but you're still down to less than 2% of humans. Of that, pick any ordinary dealbreaker; opinions on having children, political opinions, religious preferences, personal habits, and so on. Find the intersection of these. And don't forget to consider that a not-insignificant proportion of the population are simply high-functioning maniacs who you're better off never coming into contact with. And now consider mutual attractiveness.