Jaymatt
If your point is that for us as a community it is worth it to allow a number of girls to go unmatched due to the fact that an age gap of this magnitude is necessary I don’t have anything to say. Your proof from chazal is rather weak. However chazal do say that at 18 one must start to look for a wife and they do not say noce things about one who is not married by 20. In addition the Shulchan Aruch says that one who is older than 20 and not married is mevatel a mitzvah every day.
In order to show that there is a problem we need two things the average age gap and the growth rate. Which one of these do you have a problem with? The theory can be bolstered by looking at the ratio of older girls to boys in shidduchim databases however this is not necessary.
Although it would be nice to have more complete data a ten year global census is both impractical and not necessary. Statistical derivations are adequate.
As for your point about statistics I assume you advocate the use of statistically derived medical data as well as pharmaceuticals whose efficacy has been statistically validated. I imagine your point is that statistics are subject to manipulation.
If you think I am manipulating numbers to make my point please tell me why you think so. I don’t want this to be true any more than you do – however if it is hiding our head in the sand is only going to make it worse.