Rational speculative bubbles: an empirical investigation of the London Stock Exchange

In recent years, a sharp divergence of London Stock Exchange equity prices from dividends has been noted. In this paper, we examine whether this divergence can be explained by reference to the existence of a speculative bubble. Three different empirical methodologies are used: variance bounds tests, bubble specification tests, and cointegration tests based on both ex post and ex ante data. We find that, stock prices diverged significantly from their fundamental values during the late 1990's, and that this divergence has all the characteristics of a bubble

Margin requirements, positive feedback trading, and stock return autocorrelations: the case of Japan

This article examines the pattern of autocorrelation of daily stock index returns in the Tokyo Stock Exchange (TSE) by estimating the two variants of the EGARCH model by Nelson (1991). We confirm the findings by Sentana and Wadhwani (1992) and Koutmos (1997) that stock returns exhibit positive autocorrelation when volatility is low but they exhibit negative autocorrelation when volatility is rather high, and that stock returns are more negatively autocorrelated after price declines than after price rises. Evidence is also found that an increase in margin requirements makes stock returns more positively autocorrelated, which contrasts with Sentana and Wadhwani (1992) who were unable to detect any effect of margin requirements on the autocorrelation of returns in the US stock market.