A paper published in the journal Sociology says the relationships of parents are in some cases more stable if the mother earns more than the father.
Dr Shireen Kanji, of the University of Leicester School of Management, and Dr Pia Schober, of the German Institute for Economic Research, Berlin, examined survey data on 3,944 British couples as their first child aged from eight months to seven years.
The researchers looked at whether the probability of relationship breakdown was different for couples where the mother earned more - defined as at least 20% extra - or the same, or less than their partners.
The researchers found no significant statistical difference in the risk of relationship break-up if the mother earned more than the father. They also found that in some instances couples were more stable if the woman earned more. For instance:
- In the period between when the child was about four and seven, the risk of divorce for married couples where the mother earned more than the father was 80% less than for married couples in which the father was the main earner.
- In the period between when the child was about four and seven, the risk of unmarried couples splitting up where the mother earned more than the father was 60% less than for couples where the father was the main earner. Here the effect was statistically less significant.
The research found that parents who earned approximately the same were no more likely to split up than those where the father earned more, and in some cases were less likely to separate. For example for couples with children of school age, the risk of separation fell by about half for those that were married, and by more for those that were unmarried.
The researchers also found that where mothers were the sole earners in the couple, this worsened the relationship if they were married, but not if they were living together. This applied to only 1.4% of couples and did not affect the main conclusion.
"Sociological and economic theories have long predicted that women's increased economic independence would undermine the institution of marriage," said the researchers. "Previous studies of married couples in the UK provided evidence that women's higher earnings increased the risk of divorce.
"We found that influential theories that a woman's higher earnings elevate the risk of divorce are unfounded amongst contemporary parents in the UK. Our findings show that equal earning, and a mother being a main earner, are not destabilising influences on relationships, even at an intense time of childcare responsibilities."
The researchers said that at some points in time mothers earning more meant "there is a lowered rather than raised hazard of relationship dissolution and that this applies to both married and cohabiting parents." The research breaks new ground in studying the stability of both married and cohabiting parents.
The researchers found that 6% of mothers of children aged less than one year earned at least 20% more than their partners, which fell to 3.8% by the time the child was around five years old. The figures for those earning approximately the same as their partners fell from 11% to 4.3% in the same period.
These results came at a time in the UK when "the potential for women to earn the same or more than a male partner has increased rapidly in recent years, in line with a steep rise in mothers' labour force participation and women's educational performance overtaking that of men.
"However, these results do not necessarily signal a victory for gender equality. Mother-main earner and equal-earner couples are not at a higher risk of splitting up, but they do overwhelmingly change to a male-breadwinner model [over time]. The proportions of couples in which the mother is the main or equal earner decrease significantly as the first child ages."