The billion-dollar prediction markets industry began like a joke: Three economists walked into a bar. This was in Iowa City in 1988, long before anyone could bet on elections or Super Bowl halftime shows with their phone. The professors were trying to solve the sort of problem social scientists tackle over lunch. Why did polls get elections so wrong — and what could be done about it? Civil rights leader Jesse Jackson had just trounced Michael Dukakis in the Michigan presidential primary —