Explaining the Explanations of 100 Million Missing Women - Mechanism and Causality in Biology and Economics - page 224

Contrasting with Sen's and Blumberg's attempts to theorize the missing-women
phenomenon, Oster's and Lin and Luoh's studies are conducted by running
regressions on data to find significant statistical relations between high sex ratio
at birth and factors that might influence it. Although they intend to find the causal
power of the factors, it is not obvious whether they are concerned with finding the
true causal relationships. For instance, Oster ( 2005 , p. 1164) stated that “after one
adjusts for differences in the sex ratio at birth caused by hepatitis B, the number of
missing women (based on population estimates from 1980 to 1990) drops to 32
million” (our emphasis), but she has been cautious in using causal language in other
places. In Blumberg and Oster ( 2007 ), she used correlation (“paternal, not maternal,
infection is correlated with higher offspring sex ratios”) more often than causation.
Oster is concerned only to justify the hepatitis B hypothesis by claiming that the
causal relation is supported by relevant correlations. Similarly, although Lin and
Luoh found that cultural factors are causal to the missing women and they claimed
that the biological mechanism is ruled out, they could not, or would not, find the
true causal mechanism.
We might use Trygve Haavelmo's ( 1944 ) famous mechanical analogy to
illustrate. We could derive the functional relation between the pressure on the
throttle and the speed of a car on a flat road under usual conditions, but such a
relation will break down as soon as there is a change in any working part of this
car, or a change in an external condition. The throttle-speed relation is less
autonomous because this type of relation is not invariant to changes in the
surrounding conditions and thus is not fundamental to economics. For Haavelmo,
the general laws of thermodynamics and the dynamics of friction are examples of
highly autonomy relations, because they “describe the functioning of some parts
of the mechanism irrespective of what happens to some other parts” (Haavelmo
1944 , p. 28). The real automobile mechanism is hard to be discovered without
opening the hood, one might still be able to find out what causes the throttle/speed
relationship to break down. The econometric studies of Oster and of Lin and Luoh
focus on economic relations such as the one between throttle pressure and speed;
they are interested in whether or not certain relations sustain, rather than opening
the hood and seeing the engine of the car. They intend to find factors that causally
relate to sex ratio at birth, empirically speaking, and use the empirical finding to
vindicate or repudiate hypotheses.
5 Causal Structure and Net Result
Given Lin and Luoh's empirical result that the effect of hepatitis B on an increase in
the sex ratio at birth is limited, we might conclude that economists are no longer
willing to endorse the idea that hepatitis B has the efficiency to affect the sex ratio.