Comovement and Changes to the FTSE 100 Index

Abstract:     
We employ the Barberis, Shleifer and Wurgler (2004) methodology to investigate the impact of changes to the FTSE 100 index on return comovement over the 1992-2002 period. For FTSE stock inclusions the average increase in the beta coefficient is 0.38 in univariate regressions for weekly returns and 0.60 in bivariate regressions that control for the return on non-FTSE stocks. Stocks deleted from the index display the opposite pattern post exit. The results are robust to a number of factors including size, industry and non-trading effects. They are difficult to explain within a classical framework but complement those found for the US and Japan in supporting behavioral finance views of comovement.

Keywords: Behavioral finance, trading-based comovement, index funds

JEL Classifications: G11, G12, G14

Working Paper Series