The often-cited rule of half one's age plus seven years tends to hold relatively true to male preference. However, a 2013 survey suggests that the ideal age gap between older men and younger women is 4 years and 4 months, says the Date Report.
While it is socially acceptable to date within a wide age range, a number of factors play into the dynamics of relationships and attraction. While men skew younger in terms of the women about whom they fantasize, they're much more conservative when it comes to choosing real partners, says Psychology Today.
Reproduction also comes into play. Older men have children successfully with younger women after being in a relationship for a number of years; they are able to take their time. If an older woman wants to have children, she is at a slight disadvantage in terms of how much time she can spend reaching that point, states the Date Report. Women have a shorter reproductive span during their lifetimes.