What's important here is that what you have here is only one side of the coin.
If you're looking at the performance of only those who make it successfully, what you don't know is how the people who didn't make it through the process would perform on a comparative basis.
For example.... There's a pool of candidates, 90% weak, 10% strong (weak and strong if they were measured post-hiring). If your recruitment process took that ratio and ensures you hire 50% weak and 50% strong, that's obviously not completely wasted effort.
If you're looking at the performance of only those who make it successfully, what you don't know is how the people who didn't make it through the process would perform on a comparative basis.
For example.... There's a pool of candidates, 90% weak, 10% strong (weak and strong if they were measured post-hiring). If your recruitment process took that ratio and ensures you hire 50% weak and 50% strong, that's obviously not completely wasted effort.