AbstractThe University of ManchesterAdeola Deji-OloweDoctor of Philosophy (PhD)Essays on the Impact of Investor Trades in a Limit Order Book MarketNovember 2013This thesis consists of three essays examining the impact and consequences of the trading behaviour of a finely disaggregated category of investors in an electronic limit order book equity market, the Malta Stock Exchange (MSE). The three essays in market microstructure are closely related and examine how investor heterogeneity impacts the informational content of the limit order book, the informational content of individual trades, the price impact of investor trades, the aggressiveness of order submission strategies and the price discovery process within such a market. The first essay investigates the role of the financial intermediary in the price discovery process in a limit order market. We address this issue by analysing the trades of brokers within the Malta Stock Exchange by comparing the profitability of their individual trades and the impact of these trades on the price discovery process. The results of a Weighted Price Contribution methodology indicate that more active brokers that dominate the market in terms of volume and amount traded account for a significant portion of the price discovery process. We also find that the level of profitability of these brokers is directly proportional to the amount of volume traded and their relative share in the price discovery process. This appears to rule out the possibility of manipulative trades by these brokers in order to influence profitabilityThe second essay examines the price impact of the order flow emanating from finely disaggregated classes of investor with the aim of determining whether detectable differences exist in the extent to which orders emanating from particular groups of investors impact on the evolution of stock prices. On the aggregate stock level, results indicate price impact is inversely related to liquidity and as such the price impact of trades is of a higher magnitude and significance in stocks that are less liquid. Significantly, we find that stocks with higher liquidity and trading volume adjust quickly to price changes and the cumulative impact is realised earlier for these stocks. Similarly, for investor classes, our results show that the magnitude and significance of individual price impact increases as liquidity of the stocks declines, showing that as liquidity increases in the order book, the impact of information asymmetry begins to diminish. Institutional investors consistently have the highest significant impact on the evolution of prices across all the stocks. The final essay examines how investors structure their order submission choice in response to changes in the limit order book and market conditions (such as order depth, volatility, returns, and height of the limit order book). We identify 7 distinct investor classes who differ in their trading requirement and the information set available to them, and as such we expect that these investors will adopt different strategies to maximise their trades. The results show variability in the submission strategies adopted by investors as trade sides changes from buy to sell trades. It also indicate that investors have to balance between execution risk, the timely use of private information and the risk of being picked-off by other informed investors. In analysing the varied responses of these investors, we find that the order submission strategies adopted is most responsive to the risk of non-execution.