Researchers at the Institute for Social and Economic Research at the University of Essex asked both individuals in the couple to rate their happiness on a seven-point scale -- one being extremely unhappy to seven being perfect.
The study found 90 percent of married women and 88 percent of cohabiting women say they are happy in their relationships, while 93 percent of married men and 92 percent of cohabiting men said they were happy in their relationship.
The findings indicate the happiest couples are those in which both have a college degree, have no children, have been together for less than five years and the man is employed.
After accounting for age, gender, number of children, relationship duration, employment status and education married people were happier than their cohabiting counterparts, the researchers say.
The findings are part of a larger study, "Understanding Society: Early findings from the first wave of the United Kingdom's household longitudinal study."