> As the manager of the ETF you could allow it to float freely in which case it could trade at a premium or discount to NAV. ETFs are securities that trade fre

> As the manager of the ETF you could allow it to float freely in which case it could trade at a premium or discount to NAV. ETFs are securities that trade freely. They may be open ended or closed ended, but the price of both is determined independent of NAV. > But it wouldn't move too far because this would attract arbitrageurs who would trade the ETF against the individual stocks and bring it back in line. This is the creation/redemption mechanism and is actually responsible for keeping the market cap of open ended ETFs in line with the NAV. Closed ended funds don't have such a mechanism, so the cap may diverge from the NAV. > Another way you could do this is hold a pile of units in reserve and actively sell into the market when the ETF trades at a premium and buy when it trades at a discount. This approach would not result in any volume in the individual stocks (except for re-balancing from time to time). This defeats the tax advantages of the ETF structure. Instead of having the manager buy and sell names, APs (authorized particpants) do the trading, hedging with units of the ETF. They then do an in-kind exchange with the fund manager at the end of the day. If the AP has net purchased the underlying basket, they will exchange the basket for shares of the ETF (creation). If the AP is net short the basket, they will exchange their offsetting ETFs for the underlying basket (redemption). This should affect the volume of the constituents. Some ETFs do not require creation and redemption to be done with the full basket of index members. These tend to be based on names that trade less frequently. In this case the manager allows a subset of the index to be exchanged. In this case, the creation/redemption mechanism will not necessarily affect the volumes of all members of the index. Note that this can could cause tracking error. Managers will rebalance when the index the fund is based on changes. For example, bond ETFs generally rebalance once a month. Market cap weighted ETFs (as opposed to, for example, equal weighted ETFs) are easier for managers as well, because the fund doesn't need active rebalancing.