http://en.wikipedia.org/wiki/Dividends

Dividends are, crudely, the amount of company value (usually, but not necessarily, profit) that the board decides to pay equally to each equivalent share after a period of trading (usually one year, but rules vary by country).

The basic rule is that for all equivalent shares, the dividend is shared equally. That is what you own, when you own shares - the right to receive dividends and the right to vote on the election of the officials who administer the 'pool'.

You also may buy or sell those shareholder rights. And there is the problem.

What was originally a bet that required waiting until the horses had run to find out if you had backed a winner, has become a crazy melée of punters desperately trying to sell each other their betting tickets while the race is still being run. These transactions do not add anything to the pool.

You can't be me, I'm taken