we should call them probability markets. You will not be the first.

http://groups.google.com/group/Prediction-Markets/browse_thread/thread/26e6b76b4537cce9/3514dbddf76636f6?pli=1

“Still, the predictions markets did forecast a Republican Senate. Should
we dismiss them for getting that one so wrong?

If you think so, then you’re probably forgetting the principles of
probability. Prediction markets do not make absolute predictions about
electoral outcomes, economic developments, product success, or anything
else. Instead, their predictions are mere probabilities. That’s one
reason why the markets expected the Senate to stay in Republican hands,
even though so many Democratic candidates were favored. Senator-elect
Jim Webb had roughly a 60 percent probability of success, and
Senator-elect Bob Casey Jr. had roughly a 70 percent chance of success;
but these numbers do not suggest that both candidates were likely to
win simultaneously.”

—

“Perhaps we should add ‘probability markets’ to the taxonomy… “

Chris,

there is no such thing as “inaccurate predictions”, as markets express a probability, not a prediction. Degree of accuracy is what you’re looking for and it is a statistical phenomenon.

One can’t make any conclusions based on 1 or 2 markets, 1 election even, no matter how motivated people are. All it tells us, is something about these people judging prediction markets – their motivation, their lack of knowledge.

Market efficiency and accuracy are closely linked/intertwined.