An examination of minimum tick sizes on the Tokyo Stock Exchange

In setting a minimum tick size, exchanges balance the competing objectives of lowering transaction costs and encouraging liquidity provision by minimizing stepping-ahead risk. We examine the trade-off between these two types of costs by examining the proportion of time that the quoted spread equals the minimum tick size (PTIMEMIN). We undertake this analysis on the Tokyo Stock Exchange, a market that sets nine different tick sizes based on stock price. PTIMEMIN varies markedly across stocks, ranging from almost 0 to almost 100 percent. We find that trade size, the number of trades, and price are the most important determinants of whether the minimum tick size is a binding constraint. In fact, trade size and number of trades are more significant determinants of tick size constraint than price. Consequently, we argue that tick size should be set based on trading activity and price, rather than price alone.