Stephen Saad's Aspen Pharmacare, Africa's largest producer of generic medicines, has been on a tear. Its stock shot up 75% in the past year, which Saad attributes to booming business in Asia and Australia. As a result, his net worth is up by more than $500 million from a year ago. Aspen Pharmacare manufactures drugs in 17 factories including in several African countries, Australia, Mexico, Brazil and Germany. In April, Aspen hosted a 150-mile bicycle race to raise money for pediatric healthcare in South Africa, which Saad completed. He became a millionaire at age 29 after he sold his share in the drug business Covan Zurich for $3 million. He spends his free time at Exeter, his private game reserve at Sabi Sands, which is adjacent to Kruger National Park, the largest national park in South Africa.