The spirit of the Nobel Prize can be extracted from Alfred Nobel's will:
"The whole of my remaining realizable estate shall be dealt with in the following way: the capital, invested in safe securities by my executors, shall constitute a fund, the interest on which shall be annually distributed in the form of prizes to those who, during the preceding year, shall have conferred the greatest benefit to mankind."
Economic forces are probably one of the major ones that modify the quality of life of every human being in this planet, and have a definite impact on poverty, hunger, health and global peace. I'm a mathematician myself; I know what a "hard" science is and by that logic, mathematics should have its Nobel Prize as well. And I agree, Economics is less hard than most economists pretend it to be. But in any case, that's not what is in question. The fact that Economics is a major agent in the way we understand "human laws" and its effect on humankind, it warrants its place in the Nobel Prizes, I firmly believe.