In studies by various researchers of men born about 1950, the Norwegians and Dutch are the tallest in the world, with an average height of 178 centimeters(about 5 feet 10 inches), followed by Swedes at 177 centimeters. Americans are next at 175 centimeters (about 5 feet 9 inches).
Preliminary government research suggests that not much has changed recently, according to Steckel. "The average height of Americans has been pretty much stagnant for 25 years," he said.
But American men born in 1850 were tallest in the world, averaging 171 centimeters, compared to 169 centimeters for Norwegians, 168 for Swedes and 164 for the Dutch.
"I think the countries that have surpassed the United States have done well in reaching nearly everyone with complete health and nutrition services," said Steckel. "The success of the Scandinavian countries in health care shows up in many measures, not just height, such as mortality rates and life expectancy."
Immigration to the United States by people with shorter average heights -- such as Asians -- can't explain why other countries have moved ahead in average stature, according to Steckel. "In the past half century, the change in ethnic composition hasn't been enough to make a significant difference in the country's average height."
And while genes play an important role in determining how tall individual people grow, that doesn't negate the results of this international research. "Overall, genetic differences cancel each other out when you compare averages across most populations. So, in general, average height is accurate in assessing a nation's health status," Steckel said.