13F filings are made by large investment managers to report their significant positions four times a year.
This list shows the top 10 big holders of BZF as of the end of 2013, and clearly Windhaven is the only holder large enough to have been making a trade this size. Depending on whom you use to track 13F filings—we’re using Bloomberg here—you can often get historical positions as well.
Again, Windhaven is obviously the big player both in the most recent trades and probably in the blip we saw in volume in 2011.
13F filings are problematic, however. Again, in a big ETF, so many shares are held by major custodians on behalf of their customers that movements of individual big players can be tough to discern.
In that case, really all you can try to gather is whether the big trade represents buying or selling. The tape doesn’t always tell us that, since, of course, every trade has both a buyer and a seller.
But we can look at the changes in the shares outstanding for ETFs to get a sense of buying pressure or selling pressure.