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  • May 2008
  • Article
  • Review of Financial Studies

Excess Comovement of Stock Returns: Evidence from Cross-sectional Variation in Nikkei 225 Weights

By: Robin Greenwood
  • Format:Print
  • | Pages:34
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Abstract

In the presence of limits to arbitrage, cross-sectional variation in periodic investor demand should be related to the degree of comovement of returns. I exploit the unusual weighting system of the Nikkei 225 index in Japan to identify cross-sectional variation in periodic demand for index stocks. Relative to their weights in a value weighted index, some stocks in the Nikkei are overweighted by a factor of ten or more. Using overweighting as an instrument for the proportionality between demand shocks for index stocks, I find a strong positive relation between overweighting and the comovement of a stock with other stocks in the index, and a negative relationship between index overweighting and comovement with stocks outside of the index. Put simply, overweighted stocks have high betas. The results suggest that excess comovement of stock returns is a consequence of an institutionalized commonality in trading behavior, rather than inefficiencies related to the speed at which index stocks incorporate economy-wide information.

Keywords

Stocks; Investment; Investment Return; Market Transactions; Weight; Performance Expectations; Behavior; Japan

Citation

Greenwood, Robin. "Excess Comovement of Stock Returns: Evidence from Cross-sectional Variation in Nikkei 225 Weights." Review of Financial Studies 21, no. 3 (May 2008): 1153–1186.
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About The Author

Robin Greenwood

Finance
→More Publications

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