B为什么是正确的？

问题如下：

Rutledge and Stosur discuss the factors that influence ETF bid–ask spreads. Stosur tells Rutledge that quoted bid–ask spreads for a particular transaction size are:

• negatively related to the amount of the ongoing order flow in the ETF
• positively related to the costs and risks for the ETF liquidity provider
• positively related to the amount of competition among market makers for the ETF

Stosur’s statement about quoted bid–ask spreads is incorrect with respect to the:

选项：

A.

amount of the ongoing order flow in the ETF.

B.

costs and risks for the ETF liquidity providers.

C.

amount of competition among market makers for the ETF.

解释：

C is correct. Several factors determine the width of an ETF's quoted bid–ask spread. First, the amount of ongoing order flow in the ETF is negatively related to the bid–ask spread (more flow means lower spreads). Second, the actual costs and risks for the liquidity provider are positively related to spreads (more costs and risks mean higher spreads); the spread is compensation to the liquidity provider for incurring these costs and risks. Finally, the amount of competition among market makers for that ETF is negatively related to the bid–ask spread (more competition means lower spreads).

A is incorrect because Stosur is correct in stating that the quoted bid–ask spread for a particular transaction size is negatively related to the amount of the ongoing order flow in the ETF (more flow means lower spreads).

B is incorrect because Stosur is correct in stating that the quoted bid–ask spread for a particular transaction size is positively related to the costs and risks for the ETF liquidity provider (more costs and risks mean higher spreads). The bid–ask spread represents the market maker’s price for taking the other side of the ETF transaction, which includes the costs and risks to carry the position on its books and/or to hedge the position using underlying securities or closely related ETFs or derivatives.