The interplay between investors' demand and providers' incentives has shaped the evolution of exchange-traded funds (ETFs). While early ETFs offered diversification at low cost, later ETFs track niche portfolios and charge high fees. Strikingly, over their first five years, specialized ETFs lose...

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...