Age disparity in sexual relationships

The "half-your-age-plus-seven" rule

Graph of the "Half-Your-Age-Plus-Seven" Rule

The "half-your-age-plus-seven rule" is one rule of thumb defining a mathematical formula to judge whether the age difference in an intimate relationship is socially acceptable Mathematically speaking, the rule is:

25% either way rule

An alternative to the "Half plus Seven" Rule listed above, there is also a less well known rule - 25% either way.
Therefore, if a male is 24, he is allowed to target females between 18 and 30.
If a male is 40, he is socially allowed to go for females between 30 and 50.

(found this in wikipedia. a very interesting read)