The model, developed from an analysis of approximately 20 years of historical residential home market value data, calculates credit enhancement requirements to support ratings on investment-grade classes of MBS. The past 20 years of data include several stressful periods in Hong Kong, such as the 1989 Tiananmen Square student protest and the 1994–1995 rise in domestic interest rates of the People’s Republic of China (PRC). The model incorporates a loan-by-loan analysis that takes into account the characteristics of each individual property, borrower, and loan.