Susan Mayer
and Ankur Sarin
Many studies document that
poorer states have higher rates of infant mortality than wealthier
states. What is less clear is how economic inequality affects
infant mortality. Susan Mayer and Ankur Sarin try to answer
this question in their Harris School working paper, “An
Assessment of Some Mechanisms Linking Economic Inequality and
Infant Mortality.”
They find that states with higher levels of economic
inequality have higher levels of neonatal mortality (deaths within
the first month after birth), but not post-neonatal mortality.
Thus, states with higher levels of inequality have slightly higher
levels of overall infant mortality.
They also find that higher levels of inequality
are associated with greater economic segregation, which in turn
is associated with higher levels of infant mortality. This effect,
however, is partially offset by the fact that inequality also
raises health care spending, which in turn lowers infant death
rates.
Study Description
The authors use vital statistics data on birth and death records of U.S. infants
born in 1985, 1987, and 1991. The data set links birth certificates of infants
born in a given year with the death records of those infants who die before
their first birthday.
The authors consider deaths occurring within the
first year after birth as well as deaths that occur within the
first 28 days after birth (neonatal deaths). About two-thirds
of infant deaths occur in the first month, including nearly all
(98%) deaths related to low birth weight and premature birth.
Other common causes of neonatal death include respiratory complications,
pregnancy complications, and complications of the placenta, umbilical
cord, or neonatal hemorrhage. Post-natal deaths are more likely
caused by accidents, Sudden Infant Death Syndrome, and congenital
malformations.
The authors estimate the
effect of a change in inequality in a state on a change in
an infant’s chances
of death. They control a state’s racial and ethnic mix,
its mean household income, the age composition of the state population,
mother’s age and marital status, and the race of the child.
Segregation and
Health Care Spending Drive Mortality- Inequality Link
The authors find that, in general,
a rise in economic inequality has significant effects on infant
mortality in the first month, and only a very small effect after
the first month. A one standard deviation rise in inequality
is associated with an increase in the probability of neonatal
death equal to 4.2% of the observed probability of neonatal death.
Inequality has a very small effect on the probability of post-neonatal
death. Thus, inequality has a modest effect on combined neonatal
and post-neonatal deaths.
What is it about inequality that
causes higher infant mortality? The authors consider three factors:
whether the effect of inequality is greater in poor than in
rich states, economic segregation, and state spending on health
care.
If an extra dollar of
income reduces infant mortality among the poor more than among
the rich, then shifting income from rich to poor parents would
lower the infant mortality rate. The authors, however, find
no evidence of this “nonlinear” effect;
an extra dollar of income does not improve the health of infants
from poor families more than infants from wealthier families.
In contrast, income inequality leads to greater
economic segregation in a state, which in turn leads to higher
mortality rates among infants. A one standard deviation increase
in economic segregation in a state is associated with an increase
in the probability of infant death equal to 4.4% of the mean
probability of infant death and 5% of the mean probability of
neonatal death. These results suggest that had economic inequality
not increased economic segregation, it would have had little
effect on infant deaths.
Finally, rising inequality typically increases
state spending on health care mainly by increasing spending on
Medicaid. This increased spending lowers infant mortality. The
authors find that the beneficial effects of increased health
care spending nearly, but not fully, offset the negative effects
of the increase in segregation. Therefore, infant mortality increases
with state economic inequality because the negative effects of
economic segregation outweigh the positive effects of increased
health spending.
Susan Mayer is dean and associate
professor at the Irving B. Harris Graduate School of Public
Policy Studies at the University of Chicago, and Ankur Sarin
is a graduate student in the Harris School.
