Carlos Slim Helu is the world's richest man for the fourth year in a row. He clocks in at $4 billion more than a year ago, thanks to surging stock prices at his financial arm, Grupo Financiero Inbursa, and at his Grupo Carso industrial and retail giant. The first Arab Billionaire is Prince Al Waleed Bin Talal with $20 billion, followed by Mohammad Al Amoudi with $13.5 billion. Both are from Saudi Arabia. As far…