We show that following a tick size reduction in a decimal public limit order book (PLB) market quality and welfare fall for illiquid but increase for liquid stocks. If a Sub-Penny Venue (SPV) starts competing with a penny-quoting PLB, market quality deteriorates for illiquid, low priced stocks,...

The U.S. equity markets recently increased the tick size from one to five cents for smaller capitalization stocks. We show that the larger tick size raised the cost for retail-sized liquidity demanding orders by almost fifty percent, and raised profits to liquidity providers by forty percent....