We study the impact on market liquidity of the introduction of a penalty for high order-to-trade ratios (OTRs), implemented by the Italian stock exchange to curtail high-frequency quote submission. We find that the fee is associated with a collapse in the quoted depth of the stocks that make up...

We measure the extent to which consolidated liquidity in modern fragmented equity markets overstates true liquidity due to a phenomenon that we call Ghost Liquidity (GL). GL exists when traders place duplicate limit orders on competing venues, intending for only one of the orders to execute, and...

We subdivide trades on the London Stock Exchange according to their reaction times. We classify an aggressive order as 'fast' if it executes against a standing limit order that is less than 50 milliseconds old. We show that fast trades are associated with smaller execution costs than slow...