Does Baby Height Predict Adult Income?
Researchers From the U.K. and Finland See a Pattern
Feb. 22, 2005 -- An infant boy's growth during his first year of life may signal his economic growth during adulthood.
Baby boys who are taller than their peers between birth and their first birthday grow up to earn more money as adults, say researchers from the U.K. and Finland. But they say their study merely shows an association between infant height and adult income; it does not say that short people are destined to become economic failures.
It may sound outrageous to peer into a baby's cradle and sum up their earning potential decades down the road. What could a couple of extra inches of height -- one way or the other -- have to do with adult income?
More than you might think, say University of Southampton professor David Barker and colleagues. They studied baby height and adult income in 4,630 men born in Helsinki, Finland, from 1934 to 1944.
"We found that boys who were taller at any age between birth and 12 years had higher incomes in 1990," write the researchers in the March issue of Archives of Disease in Childhood.
The link started before the boys were barely old enough to walk. "This association was established in infancy," says the study.
Most of the men (67%) had fathers who worked in lower-earning blue-collar jobs, not middle-class professions. But that doesn't account for the pattern.
"Irrespective of social class at birth, men who grew slowly between birth and 1 year had lower income later in life," the researchers write. "Even among boys born into middle-class families, those who grew slowly in infancy tended to have low educational achievement and to become laborers."
Possible Reasons for a Height-Income Link
Barker's team figured out a formula for adult income based on infant height. After allowing for the father's job, they found that each 2 cm increase [0.8 inches] in length between birth and 1 year was associated with a 3.5% increase in income.
Baby girls weren't included in the study. If the men's mothers had worked outside the home, that wasn't noted. Given the men's generation, employed moms were probably much less common when subjects were young.
Education also hinged on height. Overall, 19% of the men were classified with a high level of education. That included fewer boys who were short at their first birthday. Instead, more short boys grew up to work as laborers. Again, the social class of the boys' families didn't matter.
The researchers dropped another bombshell in discussing the results. "Slow infant growth may be accompanied by slow brain growth," they write.
They admit that they could be wrong about that, suggesting two other possibilities. Perhaps short adults have a harder time getting good-paying jobs. Or maybe poor nourishment and repeated illness cramps physical activity and sensory stimulation, hampering babies' futures.
But is biology the bottom line? The researchers think so.
They conclude that there may be biological processes linked to low growth rates during infancy that may lead to lifelong impairments that affect occupational status and income.