Harry Potter and the pre-orders

As I wondered earlier: there are prediction markets in which you can bet on Harry Potter living. NewsFutures puts his probability of living at [redacted; click on the link if you want to know]. You can see a chart going back to March here. It's currently half past six in England; the answer will be publicly available in five and a half hours. Interestingly, the contract pays $100 (of virtual money) if Harry lives, $0 if Harry doesn't live, and $50 in "any other case".

Also, Amazon.com reveals that the Harry-est town in America is Falls Church, Virginia, as measured by the largest number of pre-orders per capita. (Only towns with more than 5,000 people were included.) The top twenty-two cities on this list are all within fifty-two miles of a major city. (Why 52? I was saying 50 at first, but Fredericksburg, VA was just outside the cutoff.) They are:

• Falls Church, VA (Washington, 10 miles)
• Gig Harbor, WA (Seattle 44)
• Fairfax, VA (Washington 21)
• Vienna, VA (Washington 16)
• Katy, TX (Houston 29)
• Media, PA (Philadelphia 22)
• Issaquah, WA (Seattle 17)
• Snohomish, WA (Seattle 31)
• Doylestown, PA (Philadelphia 40)
• Fairport, NY (Rochester 11)
• Woodinville, WA (Seattle 20)
• Princeton, NJ (Philadelphia 45; New York 51)
• Webster, NY (Rochester 15)
• West Chester, PA (Philadelphia 37)
• Williamsville, NY (Buffalo 11)
• Fredericksburg, VA (Washington 52)
• Port Orchard, WA (Seattle 22)
• Decatur, GA (Atlanta 6)
• Larchmont, NY (New York 27)
• Downingtown, PA (Philadelphia 39)
• Canton, GA (Atlanta 41)
• Woodstock, GA (Atlanta 31)

What surprised me was that these twenty-two cities are suburbs of a small number of cities; in particular Harry Potter seems to be most popular in the suburbs of Washington, Seattle, Philadelphia, and Atlanta. I wonder if this would correlate with the fact that certain metropolitan areas are full of the type of people who order things on the Internet than others; Seattle has that reputation, at least in my mind, and they're also Amazon's home. But so do the Bay Area and Boston and those aren't represented there. (Sebastopol, sixty miles north of San Francisco, is #30; Mill Valley, fourteen miles north, is #36. Not a single town in all of New England is on the list.) I don't have population figures at hand but I would guess that the cities on this list are smaller than the average city in the sample. You'd expect to see larger fluctuations from the "average" in smaller cities. And it wouldn't surprise me to learn that these particular towns are underserved in terms of having bookstores nearb,y, compared to how many readers there are in the city, thus making it more convenient to order online. Perhaps the bookstore chains should look at this list to decide where their next locations should be?

The Harry-est states in America is a different story; you'd expect from the first list that the states with lots of suburban population -- New Jersey or Virginia comes to mind, both states with no really large city within their borders but with one just outside -- would appear high up? Perhaps -- but the winner is actually the District of Columbia. (As a city, however, D.C. doesn't even make the top 100.) The six New England states are all high up -- Vermont is the highest at #2, Rhode Island the lowest at #16.

The moral of the story is that depending on how you sample you get very different results. Of course, the whole "Harry-est cities/states in America" thing is just a silly Amazon promotion.

what happens to The Boy Who Lived? (no spoilers.)

At MSNBC's "iPredict" feature, you can vote on whether you think Harry Potter will live. (No spoilers.) There realy hasn't been any significant fluctuation since the voting started in early June.

This leads me to believe that people aren't taking the spoilers that are out there seriously (although I haven't read them, and I do not wish to), because if people knew whether Harry Potter was going to live or die you'd see a trend in one direction or the other. Then again, I suspect that prediction markets which involve actual money changing hands are better at predicting things, because people have a bit more incentive to make a correct prediction. I am not going to go seeking such prediction markets because I don't want to know the answer, and I have enough faith in prediction markets that I suspect they may know!

For what it's worth, I think he'll live -- I just don't see J. K. Rowling killing off a character loved by millions (although then again, she did kill off Dumbledore...) -- but I think that at some point it'll look like Harry will die. I don't think that he'll die and then be resurrected on the third day, but it would be kind of interesting if that happened.

What might be interesting to see is the probability, at any given moment in the book, that Harry will live. I'm inspired by the graphs at fangraphs.com, which show the probability of each team winning a baseball game after each plate appearance. (I swear this isn't a baseball blog!) It's not entirely clear what this means, though. The baseball probabilities are computed by looking at a sample of how things have gone in past games; there is only one Harry Potter. Could you compare it to other books? Could someone halfway through the book think "hmm, in most of the books I've read where it's been like this, the protagonist dies, so things don't going to look good for Harry?" But of course this couldn't be made into a prediction market, because the whole book is released at a single moment.

But what if you had some sort of medium where the story is released in pieces? Prediction markets for plot details of television shows -- even if you didn't let people trade during the episode's airing (because many TV shows air at different times in different places) -- could be interesting.