How long the richest took to turn billionaire from millionaire?

World's richest person and Amazon CEO Jeff Bezos took two years to become a billionaire from a millionaire, according to a study by betting site Betway. World's second richest person Bill Gates took five years to gain billionaire status after becoming millionaire. Warren Buffett became a billionaire at the age of 56, about 26 years after he became a millionaire.