In the biography of barenziah it mentions how it is much harder for elves to get pregnant but elves live for like 10 time longer then humans. This fits in with most other fantasy worlds in that humans are usually militarily dominant because they breed faster even though elves live longer so humans always have the overwhelming numeric advantage and also they are more physically well built. Elves often compensate with better quality weapons and more emphasise on magic but this is not enough.
So how can the Aldmeri dominion go up against much larger human armies. It does not make any sense. I think Bethesda got lazy and contradicted their own lore. It would make sense if elves bred at the same rate but they don't so....
Also people keep saying that Skyrim can't beat the Thalmor but Ysgramor managed to thrash the elves with much fewer numbers so that is another inconsistency.
Elves normally don't live 10 times longer than humans. Dark elves for example die after 130 years. (see an interview with a dark elf)

