Birth weight is not only connected to babies' health through infancy and childhood, but also to their educational and financial prospects in the rest of their lives. The new paper suggests that the minimum wage could have lasting effects not only on today's economy, but on the next generation of Americans as well.
Low birth weight is "a very serious outcome in terms of infant health and even potentially lifetime circumstances," said Robert Kaestner, an economist at the University of Illinois at Chicago and one of the authors of the paper. "Reducing the rate of low birth weight by 3 percent or 5 percent is a nontrivial feat."
Kaestner and his colleagues, George Wehby of the University of Iowa and Dhaval Dave of Bentley University in Massachusetts, used federal data from birth certificates to compare birth weights in states where the minimum wage increased to birth weights in states that did not. The vital records include data on every birth in the country, and the researchers analyzed all of them between 1989 and 2012.
There are other factors besides the minimum wage that affect average birth weights in a state, but Wehby, Dave and Kaestner found that in states where the minimum increased, birth weights were not significantly different before the increase from birth weights in states without an increase or where there was an increase only several years later. The similarities among states in the periods before increases in the minimum suggest that any differences in birth weight afterward are a result of the minimum wage, not of other factors.
The results show that an increase in the minimum wage benefited expecting mothers of all kinds, but women who were more likely to earn the minimum wage benefited more, and so did their children.
In terms of the reduction in low birth weight, babies born to mothers of color benefited about three times as much from increases in the minimum wage as babies born to white mothers.
Young women with just a high-school diploma were another group whose newborns were particularly helped by the minimum wage. Better educated women were less likely to earn the minimum wage anyway. The same also appeared to be true of older women without a good education, who presumably had had more time to gain experience on the job and were making more money.
Women without even a diploma also benefited, but less so. Many of them might have had a hard time getting even a minimum-wage job. To the extent that employers hired fewer workers due to the increased cost of labor in states that increased the minimum wage, changes in the minimum might have reduced the incomes of some of these women as well.
Wehby, Dave and Kaestner's results accord with previous research on the relationship between income and birth weight among women at the margins of the economy, including a study on the Earned Income Tax Credit published in 2010.
Another study based on a comparison of siblings in a national survey found that being born underweight reduced a person's income as an adult by about 15 percent. Together, these studies suggest that policies that increase the incomes of expecting mothers could pay off generously in the future.