In the real world, however, age differences are more conservative – the latest National Statistics show that in marriages the mean gap is only 2.2 years, with the most common gap a meagre one year. The age gap, by the way, is defined as man's age minus women's age. Sure, most women marry and cohabit with an older man, but women are increasingly in relationships with younger men, especially if they've had a long-term relationship before.