If the key to the cure lies in the diagnosis, then a solution to the euro zone crisis may be close at hand. This week - thanks to research by the hedge fund manager Boaz Weinstein - an uncanny correlation has been established between the percentage of Greek men still at home with their parents and the price of five-year credit default swaps. These swaps are derivative instruments that insure the holder against a nasty credit event such as being chucked out of the euro zone in the aftermath of an irretrievable breakdown in political negotiations. As you can see from the accompanying chart, the percentage of men between the age of 25 and 34 living at home with their parents is also high in Portugal, Italy and Spain. In fact, it more or less mirrors the economic plight of each nation: the more men still living with their parents, the higher the risk of that country's sovereign debt.