Unlike some writers, who like to draw lots of conclusions based on sometimes slim or anecdotal evidence (coughMalcolmGladwellcough), Levitt and Dubner love data–the more the better. Their stories concern macroeconomics–the study of complex systems with large populations–and they like to highlight “natural experiments,” in which some happenstance holds certain conditions constant while varying others.
For example, they examine the effect of television on children’s behavior–specifically, violent crime rates in cities which got broadcast TV at different times during the 1950s:
[D]id the introduction of TV have any discernible effect on a given city’s crime rate?
The answer seems to be yes, indeed. For every extra year a young person was exposed to TV in his first 15 years, we see a 4 percent increase in the number of property- crime arrests later in life and a 2 percent increase in violent- crime arrests. According to our analysis, the total impact of TV on crime in the 1960s was an increase of 50 percent in property crimes and 25 percent in violent crimes.
Why did TV have this dramatic effect?
Our data offer no firm answers. The effect is largest for children who had extra TV exposure from birth to age four. Since most four year-olds weren’t watching violent shows, it’s hard to argue that content was the problem…
You can read the relevant excerpt from that chapter, “Unbelievable Stories About Apathy and Altruism,” online at freakonomicsbook.com.
As you can see above, the book isn’t all charts and graphs, though it does include some relevant visual aids. My favorite is the mathematical expression PIMPACT > RIMPACT. You’ll have to read all of chapter one to understand why that’s so amusing.
And the epilogue, which recounts a totally freaky experiment involving monkeys, is unforgettable and hilarious. I first heard Levitt and Dubner tell that story when they gave a talk at my former employer in 2005, and I wish the video were online so I could share it. You’ll just have to settle for reading the book.
ADDENDUM: You can read the complete monkey experiment story online in “Monkey Business” (New York Times Magazine, June 5, 2005).