Yes,
index arbitrageurs were flat out selling stock in 1987, but only because of the monumental selling of S&P 500 futures.
Not exact matches
But the institutions had sold massive amounts of futures, and the
index itself didn't fall nearly as far because the terrified
arbitrageurs wouldn't exploit the spread.
Normally when futures were trading far enough below the
index itself, the
arbitrageurs sold short a basket of stocks that closely tracked the
index and bought an offsetting position in the cheaper
index futures.
Following our discussion, if everyone started to buy the
index, mispricings would start to develop regularly, and
arbitrageurs would be able to profit.
At this moment the futures and the underlying assets are extremely liquid and any disparity between an
index and an underlying asset is quickly traded by
arbitrageurs.