Mexican regulatory filings indicate the family has been able to increase its stake in Mexichem by reinvesting most of their dividends and proceeds from a 2005 stock sale back into the company.
Del Valle also owns closely held lender Grupo Financiero Ve Por Mas SAB and Elementia SA, which makes copper and aluminum products and is part-owned by Carlos Slim, the world's richest man according to the Bloomberg Billionaires Index. He controls all three stakes through his holding company, Grupo Empresarial Kaluz SA. Del Valle's personal assistant said he was unavailable for comment.
Precious Peruvian Metals
Buoyed by surging gold prices, Alberto Benavides and his family have seen their 28 percent voting stake in Cia. de Minas Buenaventura SA, Peru's biggest producer of precious metals, jump five-fold in a decade to $2.7 billion. Today Benavides, 91, owns $1.2 billion of the company's stock after giving the rest in equal parts to his five children last year.
Based on an analysis of dividends, local taxes and market performance, the Benavides family probably has an investment portfolio worth at least $250 million. "We're people who have no interest in ostentation or luxury," Roque Benavides, who has led the company since his father retired, said in an e-mail. "We're working people whose goal is to contribute to the social development of Peru."
Alvaro Saieh, 62, became a billionaire after his shares of Corpbanca, Chile's sixth-biggest lender, jumped 63 percent in 2009, more than doubling the following year. His 63 percent stake is now worth more than $2.1 billion.
Saieh, who earned a doctorate at the University of Chicago and traces his roots to Palestine, formed his company by leading the takeover of century-old Banco de Concepcion in 1995 and using it to buy up rivals.
In December, Saieh oversaw the $1.16 billion acquisition of Banco Santander SA's Colombian unit, helping Corpbanca become the first Chilean financial institution to own a foreign bank.
A press official representing Saieh, who asked not to be named due to internal policy, said his closely held retail, insurance and media assets are worth $2.6 billion not including debt. SMU SA, his chain of supermarkets and retail stores, reported 2010 sales of $2.2 billion.
The number of billionaires that remain uncovered is difficult to quantify. "It's hard to give you a number. You should question anyone who claims they can," said Anthony DeChellis, head of Private Banking Americas for Credit Suisse in New York. "It is a very difficult thing to know."