  This paper analyzes correlations in patterns of trading of different members
of the London Stock Exchange. The collection of strategies associated with a
member institution is defined by the sequence of signs of net volume traded by
that institution in hour intervals. Using several methods we show that there
are significant and persistent correlations between institutions. In addition,
the correlations are structured into correlated and anti-correlated groups.
Clustering techniques using the correlations as a distance metric reveal a
meaningful clustering structure with two groups of institutions trading in
opposite directions.
