What does "no predictive power" mean? The Emperor's Nose technique has a certain amount of predictive power: it's very unlikely that it will be off by more than

What does "no predictive power" mean? The Emperor's Nose technique has a certain amount of predictive power: it's very unlikely that it will be off by more than an inch, for example. Similarly, in the hands of a conscious reader such as myself, my tarot deck has lots and lots of predictive power. Right now it tells me that Mike Gravel does not have a 50% chance to become President this year, that Barack Obama will not live to be 200 years old, and that Bill Clinton, with 99.999% certainty, has not invented a perpetual motion machine. I'm not saying these markets are wrong. I'm suggesting that, at best, they're as correct as an off-the-cuff guess by the average reader of the New York Times. That's not all that impressive, but it's just good enough that I can't consistently outguess them without doing some research -- and, given that the total size of most of these penny-ante markets is less than a postdoc's annual salary, I'm never going to make any money doing that.