Sociologists have long firmly held that marital bliss is high in the very early years of marriage, declines with the coming of children and rises in later years when children have left home. Happiness thus follows a U-shaped trajectory over the life of a marriage, as shown in the chart.
This belief derives largely from studies that employ a technique--the cross-sectional survey--unsuited to constantly changing phenomena such as marriage because it measures attitudes at only one point in time. A better method is the longitudinal study, which measures attitudes at several points in the life course. Two newer studies employing the more powerful technique now challenge the traditional U-shaped curve of marital happiness.