When I get older, I will be stronger..

K'naan knew what he was talking about when he penned his lyrics. A recent article in the economist explains that happiness follows a "U-bend" throughout one's life.  We start out happy as we're discovering life, things go down hill from youth to middle age, then we get cheerful again.

What makes people happy? Four main factors: gender, personality, external circumstances, and age.

Gender
Women are generally slightly happier than men, although more susceptible to depression.
Personality
Two personality traits shine through: neuroticism and extroversion. Neurotic people— prone to guilt, anger and anxiety—tend to be unhappy. Neurotic people are not just prone to negative feelings: they also tend to have low emotional intelligence, which makes them bad at forming or managing relationships, and that in turn makes them unhappy. Extroverts - those who like working in teams and who relish parties tend to be happier than those who shut their office doors in the daytime and hole up at home in the evenings.

External Circumstance
All sorts of things in people’s lives, such as relationships, education, income and health, shape the way they feel.

Age
Yes. Age. As the U-Bend shows, people reach their lowest point sometime in their forties and experience their happiest years in the beginning and end of their lives. But could the U-Bend be a result of growing up in different eras? The accumulation of data undermines this effect. Americans and Zimbabweans have not been formed by similar experience, yet the U-Bend still appears in both countries.

So, the moral of the story is: the older we get, the brighter we become. I'm betting that as the world's grey-haired population increases,  this will have a positive effect.