Reason of Happiness

It is believed that Americans are one of happiest and richest populations of the world so they smile very often. I've never been in the USA. I've just heard about it. But Indians and Chinese are happy and friendly people too. But they haven't much money. I just want to understand which the reason of happiness. It is believed that Russians are rude and they seldom smile. Unfortunately it is partly true. But it is just trait of Russians. Population of this country don't drink vodka with bears, few people of them can play the balalaika etc. These are stereotypes. But Russians smile very seldom. It's the truth. The friendliness is very important thing in our life, in life of mankind. My respected singer Bob Marley just before his death said to his son: "Money can't buy life". I think he understood life. He had lived great life. I've wrote many words but I haven't answered at my main question... What is the reason of happiness? If someone knows the answer explain me))) Correct me, please...