A large empirical literature is emerging on the determinants of happiness and mental
well-being. As would be expected, this topic has attracted attention from medical
statisticians, psychologists, economists, and other investigators (including recently
Easterlin 2003, Blanchflower and Oswald 2004, Helliwell and Putnam 2004, Lucas et
al 2004, Layard 2005, Smith et al 2005, Ubel et al 2005, Gilbert 2006, and Kahneman
et al 2006). However, a fundamental research question remains poorly understood.
What is the relationship between well-being and age?
There is an important difficulty with the U-shape conclusion. A variable that
measures how old someone is may be standing in for omitted cohort effects (earlier
generations may have been born in, say, particularly good or bad times). Hence the
U-shape in age could be an artifact of the data