Using data from the World Health Organisation, researchers in Malta analysed and compared the male to female ratio in Europe and North America over 50 years.
Europe was banded by latitude into Southern countries, Central Europe, and Nordic countries. The North American continent was divided by latitude into Canada, the United States, and Mexico.
They found that significantly more boys were born in southern countries, such as Greece, Italy, and Spain than in central Europe or the Nordic countries. In contrast, a low male to female ratio was found in Mexico, a higher ratio in the United States, and an even higher ratio in Canada.
The authors are unable to explain these findings, but stress that a temperature related effect cannot account for the differences.