[vomjom]

There are many obvious problems with this argument:

1. The 80% number seems to be pulled out of the air. It could be a counting error or a statistical aberration of that class, and the real Harvard number could revert to the mean.

2. The type of parents who could send a child to Harvard is a biased sample of the general population. It will mostly tend towards rich, white (or asian) families, who generally will have less children.

There's definitely not enough information to infer that first-borns are any different.

[antidaily]

Or maybe if they're not rich, they can't afford to send child #2 there.