David Hamilton Koch was an American businessman, political activist, philanthropist, and chemical engineer. In 1970, he joined the family business: Koch Industries, the second largest privately held company in the United States. He became president of the subsidiary Koch Engineering in 1979, and became a co-owner of Koch Industries in 1983. Koch served as an executive vice president of Koch Industries until he retired due to health issues in 2018. Koch was a libertarian. He was the 1980 Libertarian candidate for Vice President of the United States and helped finance the campaign. He founded Citizens for a Sound Economy and donated to advocacy groups and political campaigns, most of which were Republican. Koch became a Republican in 1984; in 2012, he spent over $100 million in a failed bid to oppose the re-election of President Barack Obama. Koch was the fourth-richest person in the United States in 2012 and was the wealthiest resident of New York City in 2013.