GDP-weighted就没有bum problem了吗？

问题如下：

The global bond benchmark in Exhibit 3 that is most appropriate for Kiest to use is the:

选项：

Global Aggregate Index.

Global High Yield Index.

Global Aggregate GDP Weighted Index

解释：

C is correct.

Kiest has a young workforce and thus a long-term investment horizon. The Global Aggregate and Global Aggregate GDP Weighted Indexes have the highest durations (7.73 and 7.71, respectively) and would be appropriate for this group. Hudgens also wants to avoid the "bums" problem, however, which arises as a result of a market-cap-weighted portfolio increasing the weight of a particular issuer or sector that has increasing borrowings. The Global Aggregate Index is a market-cap-weighted index. As a result, the Global Aggregate GDP Weighted Index is the most appropriate selection for Kiest.

我记得书上写着以市值加权容易有bum problem。但是GDP加权不也是哪个GDP占比大，投的就多。这样不是也有bum problem吗？