Chapter 7had ever been convicted of an offence by the age of 30.^3 We
can then estimate what factors affect the probability of hav-
ing a criminal conviction. The factors we examine are all
three dimensions of childhood development, as well as eth-
nicity, mother’s age and education, and whether the father
was still present when the child was 10.^4
Child development is measured at age 10 as follows. In-
tellectual performance is measured by scores on math and
reading; behavioral development by 10 questions answered
by the mother; and emotional development by 9 questions
answered by the mother. As usual, all the child development
variables are measured in standardized form. But in this
chapter they are measured in the reverse direction, so that
we can see more easily whether bad child development has
a positive effect on crime.
The results are in the first column of Table 7.1. They are
large effects, given that only 12.5% of the total sample have
been convicted. The largest effect is that of behavioral prob-
lems at age 10. Someone who is one SD worse- behaved is
3.4 percentage points more likely to become convicted. This
means that his or her chance of a conviction has increased
by a factor of 27%. Note that this is the effect of behavior
measured as early as age 10, and in fact prediction at age 16
is no more accurate than prediction at age 10.^5
Poor intellectual performance also makes a conviction
more likely. By contrast, children who are unhappy are less
likely to become criminals— perhaps they lack the desire or
energy needed for crime.