The writer of the book also thinks the comparisons are major factor - by comparing to the "stars" in a field and to those who put no effort but are just a little behind.
He also thinks parental pressure (to excel at school for example) or bad upbringing (divorces...) are the other major factor. He claims unconcious way to express this unhappiness are diets, shopping, frequent visits to the Four Floors and SPG huntintg (ie "promiscuity"), agression ...
re: surveys
I did not say I take the book or that survey as something precise. They just give insight on a point of view on life.
I find it interesting. Kind of like "simple people go to heaven".