Structured finance went from 28% of Moody's revenue in 1998 to almost 50% in 2007, and "accounted for pretty much all of Moody's growth" during that time. According to the Financial Crisis Inquiry Report, during the years 2005, 2006, and 2007, rating of structured finance products such as mortgage-backed securities made up close to half of Moody's rating revenues. From 2000 to 2007, revenues from rating structured financial instruments increased more than fourfold. However, there was some question about the models Moody's used to give structured products high ratings. In June 2005, shortly before the subprime mortgage crisis, Moody's updated its approach for estimating default correlation of non-prime/nontraditional mortgages involved in structured financial products like mortgage-backed securities and Collateralized debt obligations. Its new model was based on trends from the previous 20 years, during which time housing prices had been rising, mortgage delinquencies very low, and nontraditional mortgage products a very small niche of the market.