For example: S&P Reverse index fumnd tracks the returns of a short position in the S&P 500 Index, or rather, the inverse of the S&P 500's total return. Although borrowing costs are not included reflected in the index, it does incorporate the effect of interest earned on the investment and on the profits from the short selling of the components of the S&P 500.

例如：反向索引fumnd跟踪S＆P在S＆P 500指数的S＆P500指数的总回报，或者说，反淡仓的回报。虽然借贷成本不包含在索引中反映，它包含的投资所赚取的利息和卖空S＆P500指数的组成部分的利润的影响。
这是google翻译的结果，抱歉我没说明是关于【 市场集中度 】的衡量指标的【逆指数】，还有就是，逆指数如何求，其表达式是怎样的？

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