According to the program "The Giant Pool of Money" that we listened to in class, one of the main causes of the large increase in demand for U.S. residential mortgage-backed securities during the early 2000s was that: the U.S. government signaled that they were going to keep interest rates low. bond yields were very high. default rates on U.S. mortgages had fallen dramatically in the 1990s. housing markets outside of the U.S. were performing relatively poorly