According to a study in France, executives and professionals are 2.6 cm (1 in) taller, and university students are 2.55 cm (1 in) taller than the national average. As this case shows, data taken from a particular social group may not represent a total population in some countries. A relatively small sample of the population may have been measured, which makes it uncertain whether this sample accurately represents the entire population. The height of persons can vary over a day, due to factors such as a height increase from exercise done directly before measurement (normally inversely correlated), or a height increase since lying down for a significant period (normally inversely correlated). For example, one study revealed a mean decrease of 1.54 centimetres (0.61 in) in the heights of 100 children from getting out of bed in the morning to between 4 and 5 p.m. that same day. Such factors may not have been controlled in some of the studies. Men from Bosnia and Herzegovina, the Netherlands, Croatia, Serbia and Montenegro have the tallest average height. Dinka people are sometimes noted for their height. With the Tutsi of Rwanda, they are believed to be the tallest people in Africa. Roberts and Bainbridge reported the average height of 182.6 cm (5 ft 11.9 in) in a sample of 52 Dinka Agaar and 181.3 cm (5 ft 11.4 in) in 227 Dinka Ruweng measured in 1953–1954. Other studies of comparative historical height data and nutrition place the Dinka as the tallest people in the world.
This gives insights into the biological mechanisms underlying how these 697 genetic variants affect overall height. These loci do not only determine height, but other features or characteristics. As an example, 4 of the 7 loci identified for intracranial volume had previously been discovered for human height.The effect of environment on height is illustrated by studies performed by anthropologist Barry Bogin and coworkers of Guatemala Mayan children living in the United States. In the early 1970s, when Bogin first visited Guatemala, he observed that Mayan Indian men averaged 157.5 centimetres (5 ft 2 in) in height and the women averaged 142.2 centimetres (4 ft 8 in). Bogin took another series of measurements after the Guatemalan Civil War, during which up to a million Guatemalans fled to the United States. He discovered that Maya refugees, who ranged from six to twelve years old, were significantly taller than their Guatemalan counterparts. By 2000, the American Maya were 10.24 cm (4.03 in) taller than the Guatemalan Maya of the same age, largely due to better nutrition and health care. Bogin also noted that American Maya children had relatively longer legs, averaging 7.02 cm (2.76 in) longer than the Guatemalan Maya (a significantly lower sitting height ratio).The Nilotic peoples of Sudan such as the Shilluk and Dinka have been described as some of the tallest in the world. Dinka Ruweng males investigated by Roberts in 1953–54 were on average 181.3 centimetres (5 ft 11+1⁄2 in) tall, and Shilluk males averaged 182.6 centimetres (6 ft 0 in).