I study an auction format called penny auctions. In these auctions, every bid increases the price by a small amount, but it is costly to place a bid. The auction ends if more than some predetermined amount of time has passed since the last bid. Outcomes of real penny auctions are surprising:...

I study a repeated mechanism design problem where a revenue-maximizing monopolist sells a fixed number of service slots to randomly arriving buyers with private values and increasing exit rates. In addition to characterizing the fully optimal mechanism, I study the optimal mechanisms in two...

Risk-neutral sellers can extract high profits from risk-loving buyers by selling them lotteries. To limit this problem, gambling is heavily regulated in most countries. I show that protecting risk-loving buyers against profit-maximizing sellers is essentially impossible. Even if buyers are...