When Massachusetts became the first and so far only US state to legalise gay marriage last year, the loudest protests came from the south. Bible Belt states such as Georgia and Alabama portrayed themselves as the defenders of traditional family values against Godless liberals in the north-east.

However, surveys of marriage and divorce across the 50 states paint a very different picture of US society. They show that the most stable families are concentrated in the easy-going north-east, while the God-fearing south has the most broken homes.