when interest rates rise, people aren’t even going to think about refinancing. But when rates fall, they run to the mortgage broker. That means that IOs rise and fall in sync with interest rates—so betting on IOs is like betting on interest rates. But the partners didn’t want to forecast rates; such outright speculation made them jittery, even though they did it on occasion. Because interest rates depend on so many variables, they are essentially unpredictable. The partners’ forte was making highly specific relative bets that did not depend on broad unknowns.
