%% Seller/market maker/ specialist..... sets the bid /ask= just like real estate; buyer may or may not pay it/ so both agree, to execute a trade. Actually closing bid ask tends to be more valuable than most timely bid ask. Don't confuse asking price[real estate/ or stocks/etfs] with a transaction= may or may not happen. Good question...………………………………………………………………………...…...…………………………………………...…………….