Earlier quoted context omitted.
I was taught in economics classes that buybacks shouldn't increase the stock price at all, which clearly isn't true in practice. It ends up being more complicated than the simple models would suggest.
How could the price not go up? I understand buybacks as reverse dilution. Each share represents a larger percentage of the company, therefore it is more valuable and it's price should be higher. Is that wrong?
The stock doesn't just vanish. It is held and owned by the company. So no, each share doesn't represent a larger percentage of the company. Unless the company retires the shares.