每一个指数由多少成分股构成？

How many constituents form the index?

IBM也是今天道指30个成分股中跌幅最大的。

IBM posted the biggest drop of the 30 stocks that make up the Dow.

今年以来，主要成分股为科技股的纳指表现要好于其他市场，纳指收于08年11月20日以来的低位。

The tech-fueled index has held up better than the rest of the market so far this year, closing at the lowest points since Nov. 20, 2008.