Authorized participants (APs) exist for all ETFs. their purpose is to make sure that the ETF mirrors the underlying assets, and to provide liquidity. Consider

Authorized participants (APs) exist for all ETFs. their purpose is to make sure that the ETF mirrors the underlying assets, and to provide liquidity. Consider a ETF that consists of a single stock. IF the stock drops, the AP will lower its Bid/offer spread, and force the ETF down to the same level as the stock. But as this is a reaction to the stock falling, there is going to be a lag between the stock falling, and the ETF falling. This doesn't mean that you can sell the ETF at a higher price, necessarily.