Why do drug dealers live with their mums?

Freakonomics:  A Rogue Economist Explores the Hidden Side of Everything
By Steven D. Levitt and Stephen J. Dubner.
(William Morrow, NY, 2005, 242 pages)

One day in 1989, at the behest of his graduate advisor, Sudhir Vankatesh, a young PhD student, strolled into a housing project on the shore of Lake Michigan carrying a multiple choice, seventy-question survey.  The first question on the survey was:

How do you feel about being black and poor?

a.  Very bad
b.  Bad
c.  Neither bad nor good
d.  Somewhat good
e.  Very good

The lifts didn't work, so he took the stairs.  On his way up he stumbled across what turned out to be a gang of junior-level crack dealers, who were using a stairwell as a base for operations in an ongoing gang war.  After a long period trying to convince them that he wasn't a threat, he attempted to read out his questionnaire.  As he would later tell his University of Chicago colleagues, the test should have looked like this instead:

a.  Very bad
b.  Bad
c.  Neither bad nor good
d.  Somewhat good
e.  Very good
f.  F--- you

After this inauspicious start, Vankatesh befriended the gang, and eventually its leader, J.T.  After two years of unfettered access to all the gang's activities, he emerged with a stack of well-worn spiral notebooks -- a complete record of the gang's financial transactions over a period of four years.  Wages, sales, dues, death benefits paid out to the families of murdered members, everything.  With such priceless documents, Vankatesh quickly came into contact with Steven Levitt, a young Chicago economist.

Steven Levitt has made a career of asking peculiar questions.  Which is more dangerous -- a gun or a swimming pool?  Do black children's names hurt their career prospects?  Do parents really matter?  With Vankatesh's spiral notebooks, he posed the question -- why do drug dealers still live with their mothers?

The book, which he wrote with New York Times journalist Stephen J. Dubner, is an anarchic, disorganised, and immensely entertaining survey of Levitt's research.  As the authors enthusiastically proclaim, the book has no "unifying theme", but is, instead, a exploration of the hidden side of conventional wisdom.

Often, the topics for analysis seem mundane.  They spend a chapter studying what conclusions can be drawn from children's names.  For instance, the parents of a child named Angel have, on average, 11.38 years of education, compared with Lucienne's parents, who have 16.6 years.  Similarly, how a name is spelt can be an indicator of parents' education levels -- Jasmyn's parents have, on average, one more year of schooling than Jassmin, and nearly two more years than Jasmine.

But their left-field analysis isn't restricted to the mundane.  Levitt gained an enormous amount of publicity from a 1999 study which concluded that rather than innovative policing strategies or police numbers, tougher gun controls or a booming economy, the single most important factor in the massive reduction in crime over the last decade had been legalised abortion.

His logic is simple.  Women who are most likely to seek an abortion -- poor, single, often minorities, and young -- are also the most likely to be those whose children would grow up to be criminals.

The controversial nature of this conclusion, if it wasn't lost on Levitt when he completed the study, was certainly reinforced after the publication of his 1999 paper.  He was called, by both sides of politics, an ideologue, a eugenicist, and a racist.

As a "rogue economist", Levitt has done remarkably well.  He has been offered jobs by both Bill Clinton and George W. Bush.  His undergraduate paper, which asked "Do more police translate into less crime?", is still cited as the rebuttal to the liberalised punishment system of the 1960s and '70s.

Freakonomics is a controversial and a provocative book.  Levitt's only real message is to encourage confrontational questions, and this is certain to secure him a permanent following.

It should be noted that the authors have a blog dedicated to expanding and defending the arguments in the book -- it is available at http://www.freakonomics.com/blog.php