Mahmoud El-Gamal believes that from the 1970s to the 2000s there has been an evolution of the industry towards "progressively closer approximations" of the practices of conventional banking, approved by "progressively smaller" numbers of jurists (with only a small group for example approving "unsecured lending" to retail and corporate customers through the "tawarruq" mode in the early 2000s). The scarcity of qualified shariah supervisors — who need to be trained in both Islamic commercial law and contemporary financial practices — has been noted. One study found the 20 most popular shariah scholars holding 621 sharia board positions, — creating potential conflicts of interest.