Reinvested dividend money; see a sibling comment somewhere in here that addresses this. If the company doesn't pay a dividend, that money has to go somewhere, so it gets accounted for in the stock price (a vast oversimplification, yes).
Share price _increases_ however only occur when the market expects the company to _grow_ revenues (profits), not sustain them. In other words, your comment isn't accurate, that would not cause the share price to increase. Only actual growth, expectation of growth, or market manipulation will cause share prices to increase.