These age preferences were confirmed in marriage records with males marrying females younger than them and vice versa.
This study used 21,245 participants between 18 and 65 years of age who were not involved in a close relationship.
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).
Differences in age preferences for mates can stem from evolutionary mating strategies and age preferences in sexual partners may vary cross culturally.
There are also social theories for age differences in relationships as well as suggested reasons for 'alternative' age-hypogamous relationships.
Age-disparity relationships have been documented for most of recorded history and have been regarded with a wide range of attitudes dependant on sociocultural norms and legal systems. Relationships with age disparity of all kinds have been observed with both men and women as the older or younger partner.
In various cultures, older men and younger women often seek one another for sexual or marital relationships.