National People's Congress vice-chairman Cheng Siwei warned that China's stock market could be overheating, the Financial Times reported. "There is a bubble going on. Investors should be concerned about the risks," Cheng said. "But in a bull market, people will invest relatively irrationally. Every investor thinks they can win. But many will end up losing." The Shanghai Index rose 130% last year and the rally is ongoing. Authorities are trying to reduce stock market speculation. The China Banking Regulatory Commission is clamping down on people who use personal loans and credit cards to buy stocks.