NEW YORK – America used to be the tallest country in the world.

From the days of the founding fathers right on through the industrial revolution and two world wars, Americans literally towered over other nations. In a land of boundless open spaces and limitless natural abundance, the nation transformed its increasing wealth into human growth.

But America’s dominance in height has faded. Americans reached a height plateau after World War II, gradually falling behind the rest of the world as it continued growing taller.

Does it really matter? Does being taller give the Dutch any advantage over say, the Chinese (men 5 feet, 4.9 inches; women 5 feet, 0.8 inches) or the Brazilians (men 5 feet, 6.5 inches; women 5 feet, 3 inches)?

Perhaps. Tall people are healthier, wealthier and live longer than short people. The same things that make you tall – a nutritious diet, good prenatal care and a healthy childhood – also benefit you in those other ways.

For several years now, economic historian John Komlos and other researchers have been trying to figure out exactly why the United States fell behind. How could the wealthiest country in the world, during the most robust economic expansion in its history, simply stop growing?

“It’s absolutely fascinating,” said Eileen Crimmins, a demographer at the University of Southern California. “Maybe we’ve reached the point where we’re going to go backward in height.”

Like many human traits, an individual’s height is determined by a mix of genes and environment. Experts agree that aside from African pygmies and a few similar exceptions, most populations have about the same genetic potential for height.

That leaves environment to determine the differences in height between populations around the world, specifically the environment children experience from the moment of conception through adolescence. Any deficiency along the way, from poor prenatal care to early childhood disease or malnutrition, can prevent a person from reaching his or her full genetic height potential.

“We know environment can affect heights by three, four, five inches,” said Richard Steckel, an Ohio State University economist who has also done research on height trends in the United States during the 19th century.

All of this means a population’s average height is a very sensitive indicator of its most vulnerable members’ welfare.

But wealth doesn’t necessarily guarantee that a society will give its children what they need to thrive. In the Czech Republic, per capita income is barely half of what it is in the United States. Even so, Czechs are taller than Americans. So are Belgians, who collect 84 percent as much income as Americans.

Komlos’ latest research paper suggests the blame may lie with America’s poor diet and its expensive, inequitable health-care system.