  We show that filling an order with a large number of distinct counterparts
incurs additional market impact, as opposed to filling the order with a small
number of counterparts. For best execution, therefore, it may be beneficial to
opportunistically fill orders with as few counterparts as possible in
Large-in-scale (LIS) venues.
  This article introduces the concept of concentrated trading, a situation that
occurs when a large fraction of buying or selling in a given time period is
done by one or a few traders, for example when executing a large order. Using
London Stock Exchange data, we show that concentrated trading suffers price
impact in addition to impact caused by (smart) order routing. However, when
matched with similarly concentrated counterparts on the other side of the
market, the impact is greatly reduced. This suggests that exposing an order on
LIS venues is expected to result in execution performance improvement.
