The European Court of Justice has ruled that gender can’t be taken into account when fixing insurance premiums. This means that, despite the fact that young male drivers have far more accidents than their female counterparts, insurers will no longer be able to discriminate. This is not necessarily good news; it probably means insuring young female drivers will cost more.

Professor David Spiegelhalter, professor of the Public Understanding of Risk at the University of Cambridge, wonders how insurance companies, wedded to their risk statistics, could find reliable indirect ways to establish an applicant’s gender should it become illegal to ask applicants to tick a male/female box when the ruling comes into effect in December 2012.

He puts forward some amusing possibilities. For example, you could be asked how many shoes you own or your shoe size. You could be asked for your testosterone level or the ratio of the length of your ring and index fingers (apparently males have longer ring than index fingers than females and the bigger the difference, the more it tends to correlate with aggressive “male” behaviours).

The absurd problem of how to find out someone’s gender without actually asking, set me thinking. I’ve had to rule out lots of possibilities because overlaps between the sexes would jeopardise accuracy. For example, asking whether you wear a skirt or trousers wouldn’t work since so many women wear trousers (I know, I know, and some men wear skirts). Questioning people about their toilet habits - lid up or lid down, that sort of thing - would obviously be too offensive. What else? Body mass index? How many neck ties you own? Too unreliable.

I know of only one sure way. Insurance companies would have to ask applicants to undertake the following test (try it at home!). Kneel on the floor and, with your elbows touching your knees, extend your forearms along the floor in front of you. Straighten your fingers. Get someone to place a matchbox on the floor just touching your outstretched finger tips. Now put your hands behind your back. If you can lean forward and retrieve the matchbox in your mouth, you are female. If you can’t reach the matchbox or topple forwards, you are male.

I appreciate that if insurance companies, ever wary about being misled, were to adopt this foolproof gender test, they would require independent verification. At the very least they’d need armies of inspectors armed with matchboxes. Not a practical proposition is it?

What proxies would you suggest to tell the sex of an applicant without actually asking?