While their cousins in the south have thrived physiologically, thanks to the comforts of capitalism, North Koreans remain as stunted in stature as they were after the Second World War. Adolescents look like children, adults like young teenagers. Nor is the height difference a slight one. After studying more than 2,300 refugees who have fled the north over the past four years, anthropologist Sunyoung Pak has found that the average young northern male is 5.9cm (2.32in) shorter than his southern contemporary. The difference for women is 4.1cm (roughly 1.62in).

'North Koreans are clearly suffering from chronic growth retardation,' said Pak, of Seoul National University in South Korea. Her studies, to be published in the international journal, Economics and Human Biology, this month, suggest that North Koreans must have suffered severe malnutrition problems virtually since Korea split into two states in 1948.

Her research shows that the only ages at which the average North Korean in her sample and the average South Korean share about the same height is from 50 to 69 years. Since height is determined during the early teenage years, this suggests that North Korea began to suffer food shortages at least by the 1960s.

'According to the economic statistics distributed by the North Koreans, the country experienced economic development up to the 1970s. But according to my data this is simply not true,' said Pak.

In the past, it has been extremely difficult to obtain information about North Korea. After Korea divided into two nations following the Second World War, the north closed its borders.

Without any North Korean statistics, Pak was forced to use the stream of refugees that regularly poured over her country's border. When they are first detained after crossing the border, the North Koreans are kept for a short period in education camps. It was here that Pak conducted her research.

The North Korean 14-year-old males in her study were on average 15.8cm (6.23in) shorter than their South Korean counterparts. Among 14-year-old girls the difference was 7.5cm (2.96in). 'The refugees possibly come from the lower classes,' said Pak, 'so they may be close to the mean height in North Korea. If this is true, then there is definitely a chronic food shortage in North Korea.'