Abstract
This dissertation consists of five separate and self-contained essays. They have been written as distinct papers. Although there is a fair amount of overlap and cross-reference in analysis and discussion, the intention is that potential readers should be able to read them separately. Essay 1: An Empirical Analysis of the Trading Structure at the Stockholm Stock Exchange.This essay describes and analyzes the trading structure at the Stockholm Stock Exchange. In the empirical part, we report stylized facts based on intraday transaction and order book data, focusing on the intraday behavior of returns, trading activity, order placement and bid/ask spread, on the importance of the tick size and finally on some characteristics of the limit order book. Our main empirical conclusions are that a) the intraday U-shape in trading activity found in earlier U.S. studies on the whole also pertains to the Stockholm Stock Exchange, b) the limit order placement also follows an intraday U-shape, c) there is no distinct intraday pattern in returns, d) the volatility and bid/ask spread seems to be higher at the beginning of the trading day, e) the tick size is economically important, and f) the price impact of an order is a nonlinear function of its quantity, implying price inelastic demand and supply. Essay 2: An Empirical Analysis of the Trading Structure at the Stockholm Options and Forwards Exchange, OM.We first describe and analyze the trading structure at the Stockholm Options and Forward Exchange, OM Stockholm. It is characterized by some interesting market microstructure features, such as a high degree of transparency in a fully computerized trading system and a possibility to submit combination orders. We also present empirically results from tests on the intra- and interday trading volume of the OMX index derivatives, both in terms of number of contracts traded and in terms of number of transactions. There is evidence of a high degree of intraday variation in trading volume and some interday variation. The extension of trading hours of the underlying stocks, during the studied period should, according to modern trade concentration models, affect the distribution of trading across the day. Although no formal test of the models is possible with this data set, we are able to shed some supportive additional light on all of these models. Essay 3: Tick Size, Market Liquidity and Trading Volume: Evidence from the Stockholm Stock Exchange. (This essay was co-authored with Patrik Sandås.)The regulated tick size at a securities exchange puts a lower bound on the bid/ask spread. We use cross-sectional and cross-daily data from the Stockholm Stock Exchange to assess if this lower bound is economically important and if it has any direct effect on market depth and traded volume. We find a) strong support that the tick size is positively correlated to market depth and c) some support that it is negatively related to traded volume. We identify different groups of agents to whom a lower tick size would be beneficial and to whom it would be detrimental. Essay 4: An Analysis of the Lead-Lag Relationship between the OMX Index Forwards and the OMX Cash Index.This essay investigates the intraday lead-lag structure in returns between on the one hand the OMX cash index and on the other hand the OMX index forwards and the OMX synthetic index forwards in Sweden. The data set includes 22 months of data, from December 1991, to September 1993. It is divided into three sub-periods. The main conclusion is that there is a high degree of bidirectional interdependence, with both series Granger causing each other. Using a Sims-test, we find that the forwards as well as synthetic forwards lead the cash index with between fifteen and thirty minutes, while the cash index leads the forwards with about ten to fifteen minutes.. This implies a longer lead from the cash index to the forwards than in previous studies. The large interdependence could possibly be due to higher transaction costs, lower liquidity in the forward market and the specific trading environments used for Swedish securities. Essay 5: Order Flow Dynamics: Evidence from the Helsinki Stock Exchange. (This essay was co-authored with Kaj Hedvall.)This essay investigates the dynamics of the order flow in a limit order book. In contrast to previous studies, our data set from the Helsinki Stock Exchange encompasses the entire order book structure, including the dealer identities. This enables us to focus on the order behavior of individual dealers. We classify the events in the order book and study the structure of subsequent events using contingency tables. In specific, the structure of subsequent events initiated by the same dealer is compared to the overall event structure. We find that order splitting is more frequent than order imitation. Furthermore, if the spread increases as a result of a trade, other dealers quickly restore the spread, by submitting new limit orders. One conclusion is therefore that there exists a body of potential limit orders outside the formal limit order book and that there is a high degree of resiliency in our limit order book market. As a logical consequence, a large dealer strategically splits his order, in order for the market to supply additional liquidity. One interpretation of our results is that a limit order book market can accommodate larger orders than is first apparent by the outstanding limit orders. Another interpretation is that a limit order book structure gives room for informed traders to successively trade on their information. A third interpretation is that prices only slowly incorporate new information.