A research piece from the University of Chicago / NY University and Princeton- this:

We find that hedge funds and small, active investment advisors are most influential per dollar of assets under management, while long-term investors, such as pension funds and insurance companies are least influential.

Here is the link to the abstract of the paper.

And here is Zero Hedge with their summary of it.

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As a ps, I know a lot of folks don't like ZH, I hope you find this piece of interest through.