How per ca-pita income of a country is measures or established?

In my view, the method which is being exercised to establish Per Capita income, is Wrong, False, unrealistic and useless, Let us see the Salaries, of President of a state, Prime Minister, of a general, of a Judge, of a teacher, of a big industrialist, of a peon, of a sweeper, of a tea boy, are all these equal? Foreign Exchange depends upon the manpower of that country who work out of their countries, Foreign investment depends upon the internal law and order and political stability and facilities, a country offers to investors. So all merits, written in the books of economics are not true and mostly are failed. Economics is a everyday knowledge which is learnt and tough everyday according to the situation. World is facing financial crisis due to managerial failure in this field. We do not need economics degree holder economists, rather world need genuine Economists, who do not bear any degree but can generate good economic, financial and monitory theories. At many forums, I have rejected the current economics, which is being tough in world known universities. These Universities are producing clerical level personals to do corruption. nothing else the Biggest Economists have done yet.