Theory on high-frequency traders (HFT) predicts that market liquidity for a security decreases in the number of HFT trading the security. We test this prediction by studying a new Canadian stock exchange, Alpha, that experienced the entry of 11 HFT firms over four years. Bid-ask spreads on Alpha...

1. Monopoly -- 2. Simultaneous quantity competition -- 3. Simultaneous price competition -- 4. Sequential competition -- 5. Regulating imperfectly competitive markets -- 6. R&D incentives -- 7. Mergers and Collusion -- 8. Bundling incentives -- 9. Incomplete information, signaling, and...