After-Hours Stock Prices and Post-Crash Hangovers
研究1987年美股崩盘后，美国证券在海外市场的盘后定价效率，发现初期能预测纽约股价但后期失效，而纽约股价变化始终有效反映在伦敦和东京的盘后交易中，表明跨市场相关性受交易成本和波动率影响。
After-hours pricing in foreign equity markets of multiple-listed U.S. securities appeared to be efficient in predicting New York prices in the weeks immediately following the October 1987 crash but relatively uninformative in succeeding months. By contrast, daily changes in New York prices appear to be efficiently incorporated in after-hours trading on both the Tokyo and London exchanges throughout the sample period. This paper suggests that the asymmetry and temporal variations in cross-market correlations are consistent with rational investor behavior in equity markets with nonzero transaction costs and time-varying share price volatility. IN THE WAKE OF the October 1987 crash, a number of studies have provided evidence of significant international linkages among national equity markets where high-frequency movements in the share price indices of national exchanges appear to induce sympathetic price movements in subsequent trading on other national exchanges.' However, the cross-market correlations are generally much larger in periods of extreme volatility and appear to subside to modest or even negligible associations during periods of more normal trading activity. Since the constituent stocks of national exchange indices are not identical, it may be that the episodic increases in correlated movements of the indices are due to changes in the actual (or perceived) relative importance of common factors in periods of unusual volatility. The thrust of this paper is to remove the issue of the disparate composition of the price indices of national exchanges by examining the prices of a set of