4. The top collar may provide little protection in a bull market, when prepayment speeds are sustained at speeds significantly higher than 100% PSA. In that environment, the bond’s value will derive from its stability outside the top collar.

5. If effective collars are indicated, it is usually easy enough to deduce the schedule speeds if information on all the tranches is available. Early PACs in the series will have the same bottom collar—the structuring collar—and varying effective top collars. One or more intermediate PACs will have the structuring collars. Later PACs will show the structuring collar as their top collar and varying effective collars for the bottom. Doing so permits first-cut comparisons with PACs offered with their structuring collars stated.