With social networking sites enabling the romantically inclined to find out more about a potential lover before the first superficial chat than they previously would have in the first month of dating, this is an important question for the future of romance.
Lets assume that in looking for partners, people care somewhat about rank and and somewhat about match. That is, they want someone ‘good enough’ for them who also has interests and personality that they like.
First look at the rank component alone. Assume for a moment that people are happy to date anyone they believe is equal to or better than them in desirability. Then if everyone has a unique rank and perfect information, there will never be any dating at all. The less information they have the more errors in comparing, so the more chance that A will think B is above her while B thinks A is above him. Even if people are willing to date people somewhat less desirable than they, the same holds – by making more errors you trade wanting more desirable people for wanting less desirable people, who are more likely to want you back , even if they are making their own errors. So to the extent that people care about rank, more information means fewer hookups.
How about match then? Here it matters exactly what people want in a match. If they mostly care about their beloved having certain characteristics, more information will let everyone hear about more people who meet their requirements. On the other hand if we mainly want to avoid people with certain characteristics, more information will strike more people off the list. We might also care about an overall average desirability of characteristics – then more information is as likely to help or harm assuming the average person is averagely desirable. Or perhaps we want some minimal level of commonality, in which case more information is always a good thing – it wouldn’t matter if you find out she is a cannibalistic alcoholic prostitute, as long as eventually you discover those board games you both like. There are more possibilities.
You may argue that you will get all the information you want in the end, the question is only speed – the hookups prevented by everyone knowing more initially are those that would have failed later anyway. However flaws that dissuade you from approaching one person with a barge pole are often ‘endearing’ when you discover them too late, and once they are in place loving delusions can hide or remove attention from more flaws, so the rate of information discovery matters. To the extent we care about rank then, more information should mean fewer relationships. To the extent we care about match, it’s unclear without knowing more about what we want.
Meteuphoric 
all this works on the assuptions that love and rommance are completerly logical;
The argument about rank assumes that people can be ranked in such way that if A thinks that B>A then, given perfect information, B must also think that B>A.
There’s no reason why this should be true. Let’s say I’m into Asian girls, then the rank of some Asian girl as ranked by me is going to be higher than her rank as ranked by someone who’s not into Asian girls. Therefore, the rank is not absolute; it depends on the person doing the ranking. Since there’s no absolute rank, you have to at least consider the possibility of B ranking A>B and A ranking B>A.
You can still take the aggregate of everyone’s personal ranking of an individual in order to assign a non-trivial desirability level.
“So to the extent that people care about rank, more information means fewer hookups.”
Nope. Part of the reason hookups happen is because of more information of desirability. When a guy pursues a less desirable girl, the girl is more willing to engage in an early, short-term hookup. When desirability is approximately the same, the girl is less willing to hookup early. And, in general, guys are willing to have short-term hookups with greater disparity in desirability.
Your thesis is only true for pairs that are approximately equal.
Several wrinkles on this. First, Nikita’s comments on different criteria is an excellent point. Without this, the stock market wouldn’t work! One reason for this is that men and women are looking for different products. Women are more often than men thinking of the long term. Many men are happy to take what they perceive as an inferior partner because they’re planning a fling or a a once-and-done situation. So there will be dates, but not relationships (sound familiar?)
But what’s most interesting to me about this post is that it investigates one aspect of the general effect of market efficiency on dating (and presumably over the long term on reproduction). Tyler Cowen has touched on this in the past as well. Many people have observed that women in large metropolitan areas become obsessively picky; yes, the 6 foot intellectual property attorney she had dinner with Monday was nice, but she knows that there is a 6’2″ M&A attorney out there, and she’s going to hold out…and she keeps holding out, until she realizes her age is narrowing her options. What keeps her from committing is that she knows there are millions of people within 5 miles of all shapes and qualities. In the US, professional women in New York are infamous for this; presumably in Oz you’d find the same thing in Sydney. Also presumably there’s an effect in men, if they’re looking for relationships and not flings (some women are just looking for flings too but not as many).
It would therefore be interesting to control for education and earning and then compare dense urban center dwellers to suburban or rural singles. That would tease out if it’s just an effect of professional urban women looking for higher education/income, longer education so people get married later, or if people are holding out because of a more efficient and larger market.
Theory of how efficient dating markets have affected genes over time:
http://thelateenlightenment.blogspot.com/2009/09/how-to-test-theories-of-average.html
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