Scarcity of Women Affects Relationships and Marriage


Groups within a society have relative bargaining power with respect to other groups when it comes to forming social relationships. Marriage is one relationship that is studied extensively.  When women are scarce relative to men, they have greater bargaining power in romantic relationships. In such a situation, the average marital age of women will be significantly lower as they will secure male commitment early due to competition among males for a long-term partner. This study tested this hypothesis and found it to be true.


Operational sex ratio (OSR) is defined as the number of sexually active males per 100 sexually receptive females. An OSR of 100 indicates a population completely balanced between the sexes. OSR is one of the key factors impacting marriage rates. Members of a sex lower in numbers are able to be selective in partner choice, while members of a sex higher in numbers face greater competition in securing a potential mate. Males look for fertile females and prefer to choose a young female. Females, on the other hand, look for males with high fidelity and socioeconomic status who have resources for her and their future offspring. OSR-based research in marriage status was conducted in this study to verify these facts.


  • The study used 2000 U.S. Census data to calculate the OSR, mean and         median male marital age and mean and median female marital age.
  • Fifty of the largest metropolitan statistical areas (MSAs) in the United States were selected. People between the ages 18 and 64 years were chosen from the census data.
  • Operational sex ratio (OSR) was calculated for every 10 women available and relationship between the OSR and marital age was determined.
  • Samples were selected to control factors like income, proportion of Hispanic, African American or Latino in each metropolitan statistical area to factor their potential impact on marital behavior.

Key findings

  • The OSR for individuals aged 18 to 64 varied from 88 in Birmingham, Alabama, and Memphis, Tennessee, to 116 in Las Vegas, Nevada, with a mean of 99.
  • As expected, there was an appreciable association between male abundance and earlier median female marital ages.
  • Female scarcity was not found to have a significant relationship to mean male marital age.


Many marriages in the U.S. end in divorce. It is likely that the marital ages analyzed in this study might not correctly reflect the median and mean age of the participants first marriage. Women in Northeastern U.S. have shifted from mainly rural areas to cities in search of white collar office careers. Similarly, men have migrated to cities in the Western U.S. building careers that are technology oriented. These additional factors might influence the results. Future research to replicate the findings of these studies, incorporating the migration of population, is required.


This study indicates that where females are low in number in a society, they will be in greater demand as life partners and are likely to marry early. In such a society, males would marry later, as they need to acquire wealth, resources and social status to be attractive to females in demand. The study can likely predict the future. For example, there will be 24 million more men than women in China by the year 2020. If these men do not marry by age 40, they have low chances of ever getting married, having enough resources, and thus will be dependent on social security in their senior years. This could be a grave social problem. The study proves that an evolutionary theoretical framework is important to foresee and decipher demographic patterns and human relationships.

For More Information:

Women Tend to Marry Early in Populations Where They Are Relatively Scarce

Publication Journal: Evolutionary Psychology, July 2010

By Daniel J. Kruger; Carey J. Fitzgerald; University of Michigan, Ann Arbor and Central Michigan University, Mount Pleasant

*FYI Living Lab Reports Are Summaries of the Original Research.
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