Groups and Wisdom III

January 20, 2007 
Posted by Jay Livingston

James Surowiecki argues for the “wisdom of crowds.” The average of the guesses of a lot of interested people will be closer to the right answer than will the guess of the smartest individual. If you want to get the answer to something, let them all bet on it and then watch where the money pushes the market.

The “wisdom of crowds” runs smack up against another concept in betting— the “smart money” — the conventional idea that some bettors are consistently more astute, while others are “punching bags.” After all, if the crowd, the majority of bettors, were usually right, they would long ago have driven the bookmakers out of business.

Ideally of course, a sports book makes money on the “vig,” the 10% surcharge on losing bets. (When you bet on a football game, you put up $11 to win $10. The point spread supposedly makes both sides equally attractive. If the bookie has the same amount bet on each side — say $1100 on the Bears and $1100 on the Saints —he’s guaranteed to make $100, collecting $1100 from the losers but paying out only $1000 to the winners.)

Sociologist Ray D’Angelo, who has studied bookies, says that yes, it’s the vig that the bookies count on. That plus a few out-of-control gamblers. But how often do the bets on the two sides of a game balance out? And what happens if they don’t?

One thing bookmakers do to correct an imbalance in betting is to change the point spread. By watching changes in the point spread, you can often tell which team the crowd likes. For example, in last week’s Bears-Seahawks game, the original line suggested to Las Vegas casinos was Bears minus 7. But bettors loved the Bears, and the line quickly changed to 8. Even that didn’t deter Bear bettors or attract enough Seahawks money. Oddsmakers continued to move the line up to 8 ½ and even 9. In the end, the crowd was not wise. The Bears won, 27-24, but their bettors, who gave up a lot more than three points, lost.

This week it’s the Saints and the Bears (not, as I nearly typed from force of habit, the Saints and the Roughnecks). And apparently the crowd likes the Saints. They opened as three-point underdogs. But today, some books have cut the line 2 ½ or 2, and one big book (Bodog.com) is giving Saints bettors only 1½ points. One Website that allows you to see the number of bets confirms this crowd preference: twice as many people have taken the Saints.

So do we follow the crowd? Or should we be “contrarians” and bet against the crowd? The contrarian view says that the bookies stay in business by being smarter than the public. Bookmakers probably also subscribe to the smart money view. That’s why Ray D’Angelo’s small-time bookmakers didn’t worry about bets from “out of control” gamblers. Those bettors were definitely not smart money.

But some bettors really are the smart money. I once heard an interview with a man who sets the line for one of the big Las Vegas casinos. He said he might not be worried by a lot of money from the general public coming in on one side. But there are particular sports bettors whose opinion he respected so much that even a relatively small bet from one of them would cause him to move the line.

My guess is that in tomorrow’s game, it’s the sheer volume of money on the Saints, not the bets of a few experts, that has pushed the line down. In any case, if you’re a contrarian, you’ll go with the Bears (also if you’re a Chicagoan, but that’s a different matter). If you believe in the wisdom of crowds, you’ll bet the Saints.

There’s one more risk in going with the crowd when their betting has moved the line — the worst-case scenario: You call up your bookie on Sunday and find that all the money coming in on the Saints has driven down the line. Instead of getting three points, the line is 2 ½. You figure, hey, it’s only a half-point, a minor consideration far outweighed by the wisdom of the crowd. You take the Saints and settle in to watch the game. It’s a close one, tied for much of the fourth quarter, right up until the final seconds, when the Bears kick a field goal to win 24-21. If you had been able to get the three points, you'd have a push. But the crowd pushed the line down to 2½, leaving you a half-point short, and you hurl your copy of The Wisdom of Crowds through the TV screen.

UPDATE: The Bears won 39-14. The bookies cleaned up, and the crowd was left to reconsider its collective wisdom.

Groups and Wisdom II

January 16, 2007
Posted by Jay Livingston

The Wisdom of Crowds by James Surowiecki begins with the story of Francis Galton at the fair. Galton, whose life spans much of the 19th century, was among other things, a statistician. He also believed in improving the human race by selective breeding. In fact, he coined the term eugenics.

At the fair, Galton noticed people submitting their guesses on the weight of an ox. Galton the statistician kept track of all the guesses— some 800 in all— and computed the group mean. Galton the eugenicist assumed that the guesses of the ignorant would detract from the overall accuracy, while the guesses of farmers and butchers would be closest to the actual weight.

When all the entries were in, the mean of the group guesses was 1197 pounds; the ox’s weight, 1198 pounds. Not even the savviest ox breeder came closer than the group as a whole.
I teach a general intro course for majors, and the first concept I want them to grapple with is the social fact. I usually start with Durkheim and suicide rates. But this semester I'm thinking of doing variations on a theme by Galton for the first day of class.

1. Bring a jar filled with M&Ms.
2. Have students pass the jar around and submit a piece of paper with their name and their guess as to the number of M&Ms. (Maybe announce that there will be a prize so as try to prevent wise-ass guesses.)
3. Collect the guesses but announce that there’s going to be one more player, the group itself, i.e., the mean of all guesses.
4. Maybe ask them to speculate on whose guess will be closest or how they think the group will do compared with the guesses of the smartest students or the students who eat a lot of M&Ms and are therefore more familiar with the subject.
5. Record the guesses, compute the mean, announce the right answer.
6. If Galton is looking down and blessing this experiment, the group mean should be closer than any individual guess, even that of the most experienced M&M eater.
I’m not sure if this really gets across the point about social facts. It does show that there is something about a group that makes it different from just the sum of its individuals, but it requires no interaction, no social influence.

On the other hand, there’s a moral to the story that I like: in order for the group to be so smart, we need the contributions of everyone, even those whose guesses were farthest off. The same principle will hold true for discussion throughout the semester. So don’t suppress an idea just because you think you don’t know enough about the topic.

Now all I need is an M&M-counting machine.

Groups and Wisdom I

January 14, 2007
Posted by Jay Livingston

On Friday, The Washington Post published an article about a plane crash that occurred twenty-five years ago. The plane hadn’t been properly de-iced, and it barely lifted off the ground before crashing into a bridge.

The moral of the story, though, is not about ice but about group structure and culture, especially as these shape lines of communication. The Post calls it “a textbook example of what can go wrong when pilots do not communicate and listen properly.” As the plane was moving down the runway, the co-pilot looked at the instrument panel and said, “God, look at that thing, That doesn't seem right, does it?” He repeated his reservation, but the pilot ignored him.

At the time, the accepted way of doing things, the cockpit culture, was an authoritarian one with the captain at the top. This culture made it more likely that the captain would not hear information coming up from others and less likely that those below would speak up loudly enough to make sure they were heard.

The pilot and co-pilot in the doomed plane were “residue of an era when fighter jocks from World War II and Korea flew for the airlines. In that gung-ho environment, captains were always right. They did not need advice, and co-pilots and other crew members often were afraid to assert themselves.”

The crash led to an industry-wide attempt to change cockpit culture. Now the pilot has a checklist of conditions and readings that he and the others must review, and he has to listen closely to what others report about these items. Hospitals have tried to put a similar system in operating rooms, and in both of these places, the last checklist item is, “If anyone sees any red flags, something they are uncomfortable with, bring it to my attention.”

There’s a more general sociological truth here, one that decades of case studies and small-group experiments have shown. Authoritarian systems are very efficient for doing routine tasks in unchanging environments. But when the situation changes, centralized authoritarian structures are accidents waiting to happen. They are inflexible, mostly because the top people are reluctant to change their ways and ideas, especially if these ideas seem to have been working. Often, people lower in the system have helpful ideas for dealing with the new circumstances, but the people at the top don’t pay attention or dismiss the ideas as unworkable. By contrast, democratic systems, with information flowing freely in all directions, are much better at adapting to change.

The Post mentions only cockpits and operating rooms. But the timing of the story is interesting. The story didn’t describe pilots and surgeons as “staying the course” despite negative information, but the Post ran it only a day or two after President Bush announced his intention to put even more effort and troops into his Iraq policy, essentially ignoring information and recommendations from a variety of other voices including members of the Iraq Study Group, the military, and Congressional Republicans, and an overwhelming majority of the US population.

(Hat tip to Mark Kleiman at The Reality Based Community for catching this story.)

The Bridge II

January 9, 2007

Posted by Jay Livingston

The Geico Washington Bridge deal (mentioned in the previous entry) is dead. The Port Authority cancelled the gecko-at-the-gate arrangement. The New York Times article does not specifically mention the Montclair SocioBlog by name, but it does refer to “the loud and swift response to the contract.” Still, we’re proud do have done our part.

The incident reminded me of a proposal some years ago to defray costs at the Statue of Liberty by charging visitors a dollar. I don’t recall how long ago this was, perhaps in the 1980s. My searches on the Internet, including Lexis-Nexis, couldn’t find any reference, probably because the proposal got nowhere fast. I do recall one politician saying something like, “It’s the Statue of Liberty. She says, ‘Give me your tired, your poor.’ She doesn’t say ‘gimme a buck.’”

What’s also interesting in this issue of the interplay of public and private is that Geico, the private corporation, may have been more responsive to public opinion than was the public institution (the Port Authority). Geico was worried about its image in the public eye. But for the Port Authority, it’s not clear whether public opinion was the decisive factor in this case of multi-causality. Even in today’s statements, it’s hard to tell whether the Port Authority really shares the view that the Bridge is a public piece of architecture not to be prostituted as an advertising vehicle. In fact, one of the arguments against the deal was economic — that the PA was selling too cheap. It’s like the old punch line, “Now we’re just haggling about price.”