Recall that positive convexity roughly means that prices move in the opposite direction to interest rates. But some securitized products such as mortgage-backed securities have negative convexity,...

Recall that positive convexity roughly means that prices move in the opposite direction to interest rates. But some securitized products such as mortgage-backed securities have negative convexity, meaning that their prices tend not to rise as quickly, and can even drop, when market rates go down.