Price and Volume Effects Associated with Changes in the Danish Blue-Chip Index: The KFX Index

This paper considers the effects of changes in the composition of the Danish blue-chip KFX index for the period of 1989-2001. Consistent with the selection criterion used for the index, there is no evidence for a stock price effect at the announcement of a change in the index. However, deleted stocks experience an abnormal return averaging –13% in a six-month period before the deletion and a decrease in trading volume and efficiency of stock prices following the deletion. For added stocks, the average abnormal return is 8% and there is no significant change in trading volume or efficiency. These long-run effects are best explained by the imperfect substitutes hypothesis or the information costs/liquidity hypothesis, suggesting that stocks in the KFX Index are exposed to a higher demand or more attention and a lower cost of trading than stocks outside the index.However, the results do not rule out the possibility that part of the stock price effect is due to the selection criterion used for the KFX Index. All in all, this paper documents that the selection criterion for and the size of an index as well as the size of the related stock market are relevant when explaining the stock market effects of index revisions.