Average penis size correlates to a country's GDP growth rate, according to a recent study.

The University of Helsinki's Tatu Westling has noticed that countries that averaged smaller penis sizes grew at a faster rate than those with larger penises.

The study revealed that every centimeter increase in penis size corresponded to a five to seven per cent reduction in economic growth.

Overall GDP was highest in countries where men had average-sized penises.

In his paper, Westling says that previous studies "concentrate on economic, social and political factors, these and many related treatments largely abstain from biological and/or sexual considerations. The aim of this paper is to fi ll this scholarly gap with the male organ."

And the reason for this bizarre correlation? Westling reckons penis length and income contribute to an individual's self-esteem. So if a man has a smaller penis, he will need more money to feel good about himself.