Share repurchases have grown significantly over the past decade or two. In fact, a recent radio commentator suggested that the current rise in share prices (both the S&P 500 and the Dow Jones averages are trading at historic highs as of this writing) is due not to superior company performance, but to the increased volume of money flowing into the stock market from corporate share repurchases.
Does this sound like a valid explanation for an increase in share prices? Why or why not?