First, it needs to be said that programming is not some black art, something arcane that only the learned few may ever attempt. It is a method of communication whereby a person tells a computer what, exactly, they want it to do. Computers are picky and stupid, but they will indeed do exactly as they are told. Therefore, each program you write should be like an elegant recipe that anyone—including a computer—can follow. Ideally, each step in a program should be clearly described and, if it is complicated, broken down into smaller steps to remove all doubt about what is to happen.

I'm really starting to wonder what percentage of the population can learn to program.

My thought it's that it's small. It's a subset of the portion of people who can learn math.

can learn under current conditions is a different question than able to learn.  I think many are able to learn...

look how many people are able to learn football thanks to an ever increasing-in-complexity Madden franchise.