TradeSports Senate Race: Were the markets wrong?

The answer, unequivocally, is no.

The suggestion that Tradesports "missed" on the control of the Senate is based on a faulty understanding of probabilities. By Election Day, Senate control really came down to three close races, Virginia, Missouri, and Montana. A probability calculator shows that if the markets accurately gave each of those races about a 60% chance of going to the Democrat, then the odds that all three would go Democratic were only 22% (0.6 to the third power). Therefore, a rational person would choose the Democrat in the individual races, but would nonetheless choose the Republicans to retain control. After all, the Republicans needed only one of those three, while the Dems needed all three. Only if we posit that the Democrats had an 80% chance to win each race would Senate control have been even a 50-50 proposition.