Answer:
Lehman Brothers was a big player in the mortgage-backed securities market.

MBS are created by purchasing a bunch of mortgages, putting them in a pool then selling shares of the pool. They work fine until a lot of people default on their mortgages, as happened when all the ARMs reset.

First answer by Jmowreader. Last edit by Jmowreader. Contributor trust: 1118 [recommend contributor recommended]. Question popularity: 4 [recommend question].