问题如下：
The firm’s policy is to rebalance a portfolio when the asset class weight falls outside of a corridor around the target allocation. The width of each corridor is customized for each client and proportional to the target allocation. Beade recommends wider corridor widths for high-risk asset classes, narrower corridor widths for less liquid asset classes, and narrower corridor widths for taxable clients with high capital gains tax rates.
For clients concerned about rebalancing-related transactions costs, which of Beade’s suggested changes in the corridor width of the rebalancing policy is correct? The change with respect to:
选项：
A.high-risk asset classes.
B.less liquid asset classes.
C.taxable clients with high capital gains tax rates.
解释：
A is correct.
Theoretically, higher-risk assets would warrant a narrow corridor because high-risk assets are more likely to stray from the desired strategic asset allocation. However, narrow corridors will likely result in more frequent rebalancing and increased transaction costs, so in practice corridor width is often specified to be proportionally greater the higher the asset class’s volatility. Thus, higher-risk assets should have a wider corridor to avoid frequent, costly rebalancing costs. Her other suggestions are not correct. Less-liquid asset classes should have a wider, not narrower, corridor width. Less-liquid assets should have a wider corridor to avoid frequent rebalancing costs. For taxable investors, transactions trigger capital gains in jurisdictions that tax them. For such investors, higher tax rates on capital gains should be associated with wider (not narrower) corridor widths.
老师总结的是：资产的volatility越高，则越容易偏离，所以越需要rebalance，所以要narrow corridor。并没有说为了减少成本而要widen corridor。所以答案错了吧？
