Decimals and liquidity: A study of the NYSE

Using a carefully constructed matched sample of control (nondecimal) stocks, we isolate the effects of decimalization for a sample of NYSE-listed common stocks trading in decimals. We find that the quoted depth as well as the quoted and effective bid-ask spreads declined significantly following decimalization. Additionally, both the number of trades and trading volume declined significantly. Stock return volatilities display an initial increase but a decline over the longer term, probably as traders become more comfortable in their new milieu. JEL Classifications: G14, G18 The theory is straightforward: As prices are quoted in smaller and smaller increments, there are more opportunities and less costs for dealers and investors to improve the bid or offer on a security. As more competitive bidding ensues, naturally the spread becomes smaller. And this means better, more efficient prices for investors