There is no magic formula for achieving a happy marriage... But researchers love nothing more than trying to get to the bottom of the chaos that is love and relationships. Well, a new study suggests that the key to a lasting marriage is all in the couple's height difference. According to the Mail Online, the research, which is based on information collected from a long-term population survey, gleaned that the greater the height difference in the couple, (with the male being taller), the happier the marriage. Researcher Kitae Sohn, from Konkuk University in Seoul, South Korea explained: "Although it has been known that women prefer tall men in mating for evolutionary reasons, no study has investigated whether a taller husband makes his wife happier. "A greater height difference in a couple was positively related to the wife’s happiness. He noted that the result "indicates a powerful impact of male height on women’s psychology, probably prepared by evolution." He added that although women tend to prefer taller men, they don't necessarily know why. He wrote: "This is similar to people favouring fatty, salty, and sugary foods without knowing exactly why: such foods are essential to survival but were scarce as humans evolved - hence craving such foods increased reproductive fitness in the past. However, he noticed that the positive effects of a greater height difference fade after eighteen years of marriage. Hmm, we still think a great smile and someone who can make us laugh will always tower over everyone else.