Yesterday’s IFOD concerned the distribution of height in the U.S. and How Many People are 7-Foot Tall? Today concerns some other aspects of height that are interesting.

Height is determined partly by genetics but nutrition and other environmental factors play an important role as well. A very important factor in determining height is nutrition and illness during childhood since that is when growth occurs. As nutrition around the world has improved and many diseases that affect children have been reduced or eradicated, average height has generally increased worldwide over the past few centuries. Evidence of the importance of nutrition and healthcare can be seen through its correlation to country income as the below chart shows (y axis is income, x axis is average height in centimeters):

Correlation between (log) income (Y axis) per capita and height (in cm – X axis) 

While height has increased worldwide, the increase has been uneven. As reported by ABC News, “people from central and southern Europe, as well as East Asia, grew taller in the last 100 years. Meanwhile there was little gain in height for people from sub-Saharan African and South Asian nations. A few countries experienced decreases in their average adult height after years of gain. Dutch men, at 182.5 centimeters (about 6 feet), and Latvian women, at 170 centimeters (5 feet 7 inches), are the tallest in the world.”

Americans have been growing taller, on average, for a few hundred years, but this upward trend seems to have pretty much topped out as there has been little change in height distribution over the past generation or two. The reason we’ve stopped growing taller is that the vast majority of our population doesn’t face the nutritional and health challenges in youth of earlier generations.

There are benefits to being tall(er) as it is “associated with enhanced longevity, lower risk of adverse pregnancy outcomes and cardiovascular and respiratory diseases, and . . . higher education, earnings, and possibly even social position” according to the study A century of trends in adult human height.

With respect to social status, this study found that “taller people achieve higher social status as a result of their increased interpersonal dominance during confrontations with competitors.” Dominance was tested in a variety of situations of pedestrians of various heights approaching each other in different settings.  The study hypothesized that “the increased dominance of taller men and women is likely to result from both perceptions of the individuals themselves and the perceptions of others.”

Studies have shown that tall people earn $789 per year per inch of height over average height.  Not a huge dollar sum individually, but when taken together its $170 billion of income moving from the shortest quartile to the tallest quartile every year. Tall people also have a slight IQ advantage.  Over half of the male U.S. Senators are over 6 feet tall. Presidents also are typically of above-average height.

Note that Donald Trump (president 45) is 75 inches tall.

It’s not all rosy for tall people, however. While over time, height has been positively correlated with health and longevity due to it’s association with good nutrition and lack of childhood disease, there is mounting evidence that in societies where nutrition and healthcare are plentiful that  being of tall stature puts one at increased risk of various cancers and other causes of mortality. This article from Slate summarized it as follows: “The fact that tall people die younger appears to be an immutable physical reality. A short person is like a Honda Civic: compact and efficient. Tall people are Cadillac Escalades. With all that extra weight and machinery, something’s just bound to go wrong.”

Additionally, being a tall female can negatively affect your birth rate.  Tall women have half the birth rate of shorter women.  But it’s not related to lower fertility.  Being a “tall” female makes it difficult finding a partner, just as being a short male is the same problem in the inverse.   In the population at large, women typically date men who are 8% taller. This is an advantage for the women below the 50th percentile, who have 99 per cent of men to choose from. A 6ft 3in woman is looking at less than 3% of the male population.

Finally, being tall can be a pain. It’s harder to find clothes and more difficult to fit comfortably in cars and airplanes. A guy I met years ago who was 6’6″ tall said that he thought most of the modern world, especially airplane seats, were designed for people about 5’10” and shorter. Being 5’9″ myself I think that seems correct.