Why do ETFs trade close to their NAV?
ETFs have a very transparent portfolio holding and predefined creation basket. This allows arbitrageurs to create and redeem units every day through the in-kind creation / redemption mechanism. Such arbitrageurs are always in the market to take advantage of any significant premium or discount between the ETF market price and its NAV by doing arbitrage between the ETF and its underlying portfolio. Thus, the open architecture of ETFs ensures that there is no significant premium or discount to NAV. At the same time, additional demand / supply is absorbed due to the action of the arbitrageurs.