A study released in 2003 by the United Kingdom's Office for National Statistics concluded that the proportion of women in England and Wales marrying younger men rose from 15% to 26% between 19.
Concepts of these relationships, including what defines an age disparity, have developed over time and vary among societies.
In females, relative youth and physical attractiveness (which males valued more compared to females) demonstrated cues for fertility and high reproductive capacity.
Buss stated the specific age preference of around 25 years implied that fertility was a stronger ultimate cause of mate preference than reproductive value as data suggested that fertility peaks in females around mid-twenties.
As well as asking participants a number of questions on mate selection criteria, they also had to provide the oldest and youngest partner they would accept.
It was found that for all ages males were willing to accept females that are slightly older than they are (on average 4.5 years older), but they accept females considerably younger than their own age (on average 10 years younger).