$3.$ Referring to the case $$Bear Stearns and the Seeds of Its Demise.$$ Baa$-$rated corporate bonds had average five$-$year default rate of $2\mathrm{.}2\%,$ whereas Baa$-$rated CDOs had five$-$year default rate of $24\%.$ Why are the default rates on the debt securities of the same rating so dramatically different?