As well as the religious aspect, customers are attracted to Islamic finance by its flexibility, link to real economic activity and its ban on transactions involving speculation or uncertainty. To meet ever-increasing demand, Islamic finance has developed numerous products compliant with sharia law, from loans for cars and houses to funding for major infrastructure projects. The industry, which spans more than 70 countries, could be worth $4 trillion by 2020, according to forecasters including Standard and Poor's. About 80 percent of the assets are now in banks, 15 percent in Islamic bonds called Sukuk, four percent in investment funds and one percent in Islamic insurance known as Takaful.