Carlos Slim, the world's richest man, lost around US$6.7 billion ($8 billion) last week.
According to Bloomberg data, Slim's stock portfolio has fallen 9.5 per cent since July 29 to US$64.4 billion. The Standard & Poor's 500 has fallen 7.2 per cent in that time.
Slim, 71, has taken a hit as Mexico's benchmark IPC index dropped 6.4 per cent and the peso slid 2.3 per cent against the US dollar. The removal of three of Slim's companies from the IPC index has made matters worse for the billionaire.
Leon Cabrera, a trader at Mexico City-based Vanguardia Casa de Bolsa, said Slim was "particularly hurt" by the companies that were removed from the IPC.
Forbes named Slim the world's richest man for the second year in a row this year. In March, the magazine put his net worth at US$74 billion and said it had grown by US$20.5 billion in the previous year, on the strength of the Mexican stock market, a strong peso, and "successful mining and real estate spinoffs from conglomerate Grupo Carso".