Mid-Day Call Auctions

Abstract

In illiquid and fragmented limit order book markets, asynchronously arriving buyers and sellers have a coordination problem. This problem is particularly strong mid-day, when trading is generally thin. We evaluate a market structure reform at Nasdaq Nordic, where the continuous trading session is replaced mid-day by a five-minute call auction. We find that the mid-day call auction works as a coordination device, reducing transitory price impact. The call auction attracts end investors rather than intermediaries. Stocks with greater end investor flows show stronger benefits of the call auction. The results indicate that mid-day auctions can improve continuous markets.