This post is inspired by today's New York Times mush piece about people's obsession with lucky numbers when looking to buy apartments.
First thought: the behavior of these real estate agents - extracting small extra fees like $500 to arrange a particular closing date - seems to contradict the Freakonomics's claim that agents have no incentive to push for small changes that affect their fee by small amounts. I don't think Levitt and Dubner are wrong--rather, that they ignored the impact of the general economic conditions; it might well be true that a few years ago, when apartments were selling like hotcakes, small amounts meant nothing but now, when apartments are not moving, the agents are more fee-hungry.
In general, that's one of the things we have to keep in mind when reading Freakonomics and similar books. At the micro level, they are telling us about unexpected effects but very often, these effects have marginal impact on the outcome--and there are other factors that have much stronger effects. Take for instance the advice to time your son's birth to make a major leaguer... if you compare two parents that did everything else the same except when they conceived their sons, then yes, the one who timed the birth might have a little advantage; but in the real world, you can't find two parents that did everything else the same, but you'll find the parents who, say, hire the better coach or send the kid to the school with the better baseball program, would stand a much better chance of producing a major leaguer.
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Second thought: lots of people who play lotteries pick lucky numbers. (The retiree who got scammed in Chapter 5 of Numbers Rule Your World bought the same set of numbers every time--a combination of the days of birth of his family.) The problem is that these numbers are not unique to you. If you're Chinese and like 8s, lots of other Chinese also like 8s. If you are born on the 10th and your wife on the 20th, lots of other couples also share the same birthdays; in fact, there are still others who'd pick 10 and 20 for other reasons unbeknownst to you.
If the numbers don't win, it's not a big deal. If they win, you find lots of company.
John Haigh's book, Taking Chances, has a lot of great insights about lotteries. For instance, why is the sequence {40 39 48 41 20 45} popular in Canada's 6/49 lotteries? It turns out that these are the 6 least popular numbers in the lottery's history, and this information is published so many players use it. (Notice the paradox: while each number individually is unpopular, the set of unpopular numbers itself is quite popular.)
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