BIS central bankers’ speeches  3  To understand the problem, we should be aware of the special role of money market funds (MMFs) in the United States. US MMFs were considered to be extremely safe financial assets. One of the primary reasons for this was that MMFs were only allowed to invest in AAA-rated assets.
Therefore, when ratings were downgraded for ABCP, MMFs did not reinvest in ABCP. Then, funds that originated ABCP and used it to raise money found themselves in fund-raising difficulties: funds under the Bear Stearns umbrella went bankrupt; BNP Paribas moved to freeze its affiliated funds’ new applications and redemptions. These funds were the structured investment vehicles (SIV) created by banks to issue ABCP.