What makes people happy?

Economist: Four main factors, explain happiness: 

• Age: Things go downhill from youth to middle age until they reach a nadir commonly known as the mid-life crisis. ... . [Then as people lose] ... vitality, mental sharpness and looks, they also gain what people spend their lives pursuing: happiness.
• Gender: Women, by and large, are slightly happier than men. But they are also more susceptible to depression: a fifth to a quarter of women experience depression at some point in their lives, compared with around a tenth of men. 
• Personality: Neurotic people—those who are prone to guilt, anger and anxiety—tend to be unhappy. ... Whereas neuroticism tends to make for gloomy types, extroversion does the opposite.
• Circumstances: Married, employed, childless, and richer people are happier