We develop a framework for assessing security market quality, relating five elements of market design to three metrics of market integrity and two metrics of market efficiency. We empirically implement this integrity–efficiency MQ framework by testing a hypothesis that trade-based ramping manipulation at the close raises execution costs on 24 security markets worldwide. Estimating a simultaneous equations model of ramping incidence, spreads, and the probability of deploying real-time surveillance, we show that quoted bid-ask spreads are positively related to the incidence (...) of MTC across seven liquidity deciles. The magnitude is economically significant; improving market integrity by cutting MTC in half reduces spreads 6–11 %. Allowing direct market access in conjunction with RTS, conducting auctions at the close, and developing regulations that require surveillance, all reduce MTC and thereby lower spreads, assuring better market integrity and enhancing market efficiency. Introducing circuit breakers or prohibiting shorts poses integrity–efficiency tradeoffs. (shrink)

Prior research suggests brokers do not always act in the best interests of clients, although morally obligated to do so. We empirically investigated this issue focusing on trades executed at best execution price, before and after the introduction of electronic limit-order trading, on the London Stock Exchange. As a result of limit-order trading, the proportion of trades executed at the best execution price for the customer significantly increased. We attribute this to a sustained increase in the liquidity of stocks as (...) a result of limit-order trading, regardless of market capitalisation. We discuss the ethical implications of our findings and conclude that market structures that enhance market competitiveness may help reconcile broker and client interests. (shrink)