Like most financial engineering techniques, securitisation is not without risk. The complexity inherent in securitisation can impair investors' ability to monitor risk, and competitive securitisation markets are prone to sharp declines in underwriting standards. Furthermore, off-balance sheet accounting treatment for securitisations coupled with guarantees from the issuer can make it challenging to assess exposures, encouraging issuers to take on excessive credit risk. Even the most ardent advocates of securitisation would accept that securitisation played an important role in the US subprime mortgage crisis that led to the global financial crisis of 2008.