The US 2000–2002 market descent: how much longer and deeper?

A remarkable similarity in the behaviour of the US S&P500 index from 1996 to August 2002 and of the Japanese Nikkei index from 1985 to 1992 (11 year shift) is presented, with particular emphasis on the structure of the bearish phases. Extending a previous analysis of Johansen and Sornette on the Nikkei index ‘antibubble’ based on a theory of cooperative herding and imitation working both in bullish as well as in bearish regimes, we demonstrate the existence of a clear signature of herding in the decay of the S&P500 index since August 2000 with high statistical significance, in the form of strong log-periodic components. In the next two years, we predict an overall continuation of the bearish phase, punctuated by local rallies; we predict an overall increasing market until the end of the year 2002 or until the first quarter of 2003; we predict a severe following descent (with maybe one or two severe ups and downs in the middle) which stops during the first semester of 2004. Beyond this, we cannot be very certain due to the possible effect of additional nonlinear collective effects and of a real departure from the antibubble regime. The similarities between the two stock market indices may reflect deeper similarities between the fundamentals of the two economies which both went through over-valuation with strong speculative phases preceding the transition to bearish phases characterized by a surprising number of bad surprises (bad loans for Japan and accounting frauds for the US) sapping investors’ confidence.