  In the Cont-Bouchaud model [cond-mat/9712318] of stock markets, percolation
clusters act as buying or selling investors and their statistics controls that
of the price variations. Rather than fixing the concentration controlling each
cluster connectivity artificially at or close to the critical value, we propose
that clusters shatter and aggregate continuously as the concentration evolves
randomly, reflecting the incessant time evolution of groups of opinions and
market moods. By the mechanism of ``sweeping of an instability'' [D. Sornette,
Journal de Physique I 4, 209 (1994)], this market model spontaneously exhibits
reasonable power law statistics for the distribution of price changes and
accounts for the other important stylized facts of stock market price
fluctuations.
