解析中The cost of higher convexity is lower yield怎么理解

问题如下：

Lee and Cook are interested in “riding the curve” over the next year in either the US or Germany and buying convexity with the use of long and short positions in calls and puts. Buying convexity will most likely:

选项：

A.

require selling puts.

B.

require buying calls.

C.

involve increasing the portfolio yield.

解释：

Correct Answer: B

Buying convexity means increasing portfolio convexity. The portfolio benefits from higher convexity when there are large changes in interest rates. The cost of higher convexity is lower yield.

Increasing convexity can be done by buying calls, puts, putable bonds, or reducing exposure to MBS and callable bonds.