As I noted in 2007-2008, despite being a relatively small piece of the equity markets (3% per the latest analysis) , hedge funds have a massive impact as the marginal buyer (or seller). We can say the same for ETFs as they only represent 4% of assets in equity markets, but are used by so much of the investment community as trading vehicles.
A lot of other tidbits here including the most widely held stocks by the hedgie community (which over the long run outperform as a group)
Our most recent Hedge Fund Trend Monitor report analyzed 700 hedge funds with $1.25 trillion of gross equity positions consisting of $822 billion of long stock-specific and ETF equity assets and an estimated $428 billion of short single-stock and ETF positions. We have published our quarterly Hedge Fund Trend Monitor for the past five years and analyzed constituent-level portfolio holdings of US hedge funds since 2001. The current report focuses on hedge fund positions at the start of 2Q 2011 and is based on 13-F filings as of May 15, 2011.
As always hit 'fullscreen' for an easier read