answers: oil
context: 2012. It tracks the 500 wealthiest people in the world. The ranking was designed to provide a more transparent and accountable presentation of the world's biggest personal fortunes. At first, the index only tracked the 20 richest people in the world, and then expanded to 100, 200, 400 and later 500 in October 2016. At its launch in 2012, Mexican telecommunications tycoon Carlos Slim was in the top spot, with an estimated $65.8 billion net worth. Beginning in May 2013, Microsoft co-founder Bill Gates was the world's top billionaire. Amazon CEO Jeff Bezos and Spanish fashion retailer Amancio Ortega both </s> John D. Rockefeller became the world's first confirmed U.S. dollar billionaire in 1916, and still holds the title of history's wealthiest individual. As of 2018, there are over 2,200 U.S. dollar billionaires worldwide, with a combined wealth of over , up from in 2017. According to a 2017 Oxfam report, the top eight richest billionaires own as much combined wealth as "half the human race". According to the "Forbes" report released in March 2017, there are currently 2,043 U.S. dollar billionaires worldwide, from 66 countries, with a combined net worth of $7.67 trillion, which is more than the combined GDP </s> 86, penned the following words to sum up his life: John D. Rockefeller John Davison Rockefeller Sr. (July 8, 1839 – May 23, 1937) was an American oil industry business magnate, industrialist, and philanthropist. He is widely considered the wealthiest American of all time, and the richest person in modern history. Rockefeller was born into a large family in upstate New York and was shaped by his con man father and religious mother. His family moved several times before eventually settling in Cleveland, Ohio. Rockefeller became an assistant bookkeeper at age 16 and went into a business partnership with Maurice
question: the world 's first billionare made his fortune in what industry