The boom in Chinese contemporary art is the result of China's opening to foreign investment and private entrepreneurship in 1978, and the significant contribution by the transnational art enterprises of long-term patron-investor-collectors, such as Uli Sigg and Guy Ullens, between approximately 1989 and 2013. Through the opportunity offered by the gap between the private market mechanism and national heritage process for the "art game", these investors used a variation of the controversial "Saatchi model" to generate high ROI. A further effect has been to bring CCA onto the global stage and complete the ecosystem of the art industry, building a foundation for the art economy of post-Mao China.