Billionaire industrialist David Koch, a driving force behind conglomerate Koch Industries who as one of the world's richest people became a major financier of conservative causes and political candidates, died August 23 at age 79. Koch, a philanthropist and patron of cultural and medical institutions, amassed his vast wealth with a large ownership stake in Koch Industries, the Wichita, Kansas-based company he ran with his older brother Charles. Koch Industries - one of the world's largest privately held businesses - aggressively expanded beyond the oil refining business their father created into an array of new ventures. He and his brother Charles, both Massachusetts Institute of Technology-trained engineers, spent hundreds of millions of dollars to back conservative causes and Republican political candidates. The brothers funded groups like Americans for Prosperity that spread their libertarian vision of conservatism advocating lower taxes and fewer regulations on businesses, and donated heavily to Republican candidates. Critics said the brothers used their riches to buy political influence and peddle positions that would benefit them financially.