  We study precursors to the global market crash that occurred on all main
stock exchanges throughout the world in October 2008 about three weeks after
the bankruptcy of Lehman Brothers Holdings Inc. on 15 September. We examine the
collective behavior of stock returns and analyze the market mode, which is a
market-wide collective mode, with constituent issues of the FTSE 100 index
listed on the London Stock Exchange. Before the market crash, a sharp rise in a
measure of the collective behavior was observed. It was shown to be associated
with news including the words "financial crisis." They did not impact stock
prices severely alone, but they exacerbated the pessimistic mood that prevailed
among stock market participants. Such news increased after the Lehman shock
preceding the market crash. The variance increased along with the cumulative
amount of news according to a power law.
