While the novel ways of thinking and viewing the world proposed by Levitt and Dubner in Freakonomics have achieved widespread popularity, it is important, as with any academic text containing an individual's own argument, to understand the criticism coming at it as well. Though Freakonomics and its authors have been praised by many, others take issue with some of the approaches used and conclusions drawn in this book.
Many critics condemn Freakonomics for making large, impactful claims without providing appropriate data to back them up. Along the same lines, it is said that the authors chose their data selectively in order to confirm the conclusions they were trying to reach, purposefully neglecting data that might lead to a different conclusion—this is a form of confirmation bias. Some critics also argue that Levitt has convoluted certain effects he discusses by coming up with causes that are far too complex, when evidence exists for a simpler, more direct explanation.
The primary argument that has come under fire is one central to both Levitt's academic research and to the book itself: that the legalization of abortion caused the 1990s crime drop. Some people have perceived it as an argument in favor of legalized abortion, though Levitt insists that it is less an argument about abortion and more an argument about crime. Economist Christopher Foote and his research assistant Christopher Goetz published a paper arguing that Levitt had made statistical errors in his abortion/crime analysis, concluding that the data was far too messy and incomplete to prove any statistically significant relationship.
Overall, Freakonomics has been criticized for allegedly sensationalizing a lot of these nuanced phenomena in order to cater his research to pop culture. Because of the controversial nature of much of its subject matter, this can be expected—regardless of the book's controversiality, however, the tools and techniques discussed are certainly important.