Mexican billionaire Carlos Slim, the world’s richest man, lost $8 billion over the last four days as Mexico’s IPC index dropped 7.4 percent. The peso also dipped 2.5 percent against the dollar amid concerns that the struggling U.S. economy will affect demand for assets in Mexico. Slim, 71, saw his stock portfolio, which is valued at roughly $63 billion, drop 11 percent since July 29. That’s more than the 7.1 decrease in the Standard & Poor’s 500 Index. Three of his companies left the IPC, making matters worse for the billionaire.