<p> This dissertation consists of two topics. In chapter 1, we develop a discrete disaggregated model in which, the market maker can observe individual order flow instead of a batch order in Kyle (1985). The model suggests that the behavior of the uninformed traders play an important role in how the informed make the optimal trading strategy : when the uninformed is more likely to use large order, the informed will also trade large, no matter what size of signal he receives, and when the uninformed tend to trade with small size order, the informed will have to trade small quantity to maximize his expected profit, even if he receives the large value signal. When the uninformed does not prefer size of order, the informed will trade smaller (larger) quantities when receiving small(large) value signals. The result is consistent with the behavior of the informed in Kyle (1985). We further investigate order flow disaggregation on market liquidity by comparing aggregated order flow structure, in which market maker observes aggregated order flow. When the model setup is symmetric, the aggregated structure can provide more liquidity, while the disaggregated structure is more liquid under the asymmetric model setup. In chapter 2, we employ the type 2 joint power law distribution in Mardia (1962) to study the joint effect of the return and trading volume. The parameter estimate for marginal distribution in joint power-law exhibits the same pattern as in univariate power law literature for return and volume, but the value are smaller due to the joint effect of return and trading volume. However, we find the joint power law shows higher predictability than the univariate power law by employing the measure MSE (Means squared error). Additionally, the type 2 joint power law indicates the linear relationship between log absolute value of return and log trading volume , which suggests the none linear impact of trading volume on price. We also find that, as sampling interval shrinks from day to 15 seconds, the price impact will increase. And also as the waiting time for two consecutive transactions shrinks, the price impact will increase, which is in line with the result of Dufour and Engle (2000). </p>

This dissertation consists of two essays. The first essay develops a new methodology for estimating the probability of informed trading from the observed quotes and depths, by extending the Copeland and Galai (1983) model. This measure (PROBINF) can be computed for each quote and it represents the specialist's ex-ante estimate of the probability of informed trading. I show that PROBINF exhibits a strong and robust relationship with the observed level of insider trading and with measures of the price impact of trades (ë) estimated based on the models of Glosten and Harris (1988), Madhavan and Smidt (1991) and Foster and Viswanathan (1993). In contrast, the alternative measure of the probability of informed trading (PIN) developed by Easley, Kiefer, O'Hara and Paperman (1996) exhibits a weaker and less robust relationship with insider trading and price impact of trades. The time series pattern of PROBINF in an intra-day analysis around earnings announcement is consistent with previous findings regarding informed trading. An important advantage of PROBINF over PIN and other measures of information asymmetry such as price impact of trades and adverse selection component of the spread is that, unlike these measures, it can be estimated for each quote, and thus can also be used to measure intra-day changes in informed trading and information asymmetry. In the second essay, I examine whether the underwriting syndicate composition influences the secondary market liquidity for initial public offerings (IPOs). Specifically, I argue that co-managers improve the liquidity of IPOs through the other services they provide, besides market making. Using a comprehensive sample of initial public offerings completed between January 1993 and December 2005, I find that IPOs with a high number of co-managers in their syndicates have lower spreads and a lower level of information asymmetry in the aftermarket. I argue that the information produced during the premarket and the analyst coverage in the aftermarket are the main channels through which co-managers mitigate the information asymmetry risk in the secondary market. / Ph. D.

O objetivo principal deste trabalho é analisar o efeito da assimetria da informação no custo de capital próprio das empresas negociadas em bolsa de valores no Brasil. O tema está em constante debate sobre a existência dessa relação e até mesmo sobre sua relação com o custo de capital ser favorável ou não. A assimetria da informação foi estimada através da Probability of informed trading (PIN), mensurando de forma direta a existência de negociações com informação privilegiada para a confrontação com custo de capital das empresas brasileiras. O resultado encontrado não apresentou relação estatisticamente significante a 5% entre a PIN e o custo de capital, de forma que não foi possível verificar a relação entre assimetria da informação e o custo de capital. Adicionalmente, o coeficiente encontrado para a PIN no modelo adotado indica uma possível correlação negativa da variável estudada e o custo de capital, deste modo o estudo corrobora com a conclusão de Lambert et al. (2012), segundo a qual, em mercados líquidos, a assimetria da informação não exerce papel relevante e sim a quantidade e a qualidade da informação disponível, não importando a forma de entrada da informação no mercado. / The main objective of this thesis is to analyze the effect of information asymmetry on the cost of equity of companies traded in stock exchanges in Brazil. It is constantly debated whether this relationship exists and also whether information asymmetry\'s effect on the cost of equity is favorable or not. Information asymmetry has been estimated using the PIN (Probability of Informed Trading), directly measuring the existence of insider trading for confrontation with the cost of equity of Brazilian companies. The result obtained did not show a statistically significant relationship at the 5% level between the PIN and the cost of equity; therefore, it was not possible to ascertain the relationship between information asymmetry and cost of equity. Additionally, the coefficient found for the PIN on the selected model indicates a possible negative correlation between the studied variable and the cost of equity, which indicates that the study corroborates the conclusion of Lambert et al. (2012), according to which information asymmetry does not exert a significant role in liquid markets but rather this role is exerted by the quantity and quality of available information, regardless of how information reaches the market.

This paper firstly constructed an order-driven market probability model of informed trading to analyze the correlation between informed trade and return of assets and the trade-price effect. Secondly, using the probability model of informed trading, we constructed a probability model of arbitrage trading in order-driven call market, which could analyze the stabilization fund and the arbitrage trade, to investigate whether the government¡¦s interference measures were necessary and whether the intervened timepoints conformed to the set-up spirit of the stabilization fund¡Xto intervene while falling and not to while rising. Finally, we set up a ratio empirical model of informed trading which could analyze the intraday trade scale of each trade section of informed traders and uninformed traders, to analyze the change of intraday trade scale of each type of investors while trade frequency changed to explore the factors of market performance. The main results are as follows respectively: Regarding the correlation analysis of informed trading and return of assets and trade-price effect, we found that (1) in the short-term (intraday, day) there was no relationship between probability of informed trading and return of assets, whereas in the mid-term probability of informed trading was correlated with return of assets although the influence impact was not as high as prior researches (Hasbrouck (1991a, b), Glosten and Harris (1988)) expected. (2) The intraday probability of informed trading of good news days was obviously higher than that of bad news days, which indicated that unbalanced buy-sell informed trade phenomenon existed in the market. Regarding the investigation of whether the intervened timepoints of stabilization fund conformed to the set-up spirit of the stabilization fund¡Xto intervene while falling and not to while rising, the main results are: (1) the individual stocks intervened by the stabilization fund had slightly smaller volatility, slightly worse efficiency, better returns and significantly larger liquidity. (2) There was no significant difference in the probability of arbitrage trading between the targets intervened by the stabilization fund and the other companies, nor in the performance (including volatility, efficiency, liquidity and return) between both. (3) The stabilization fund and arbitragers tended to conduct transactions in the opening period, which corresponds with the proposition of Schwartz (1988). (4) We also found that compared with other arbitrage trade, the trade of the stabilization fund was more correlated with the price up-down of the market, but not with that of individual stocks. In the analysis of the intraday trade scale change of each type of investors while trade frequency changed, the main findings are: (1) the slowdown of trade frequency caused smaller intraday trade ratio and worse performance in the opening, but it increased the intraday trade ratio and performance of the closing period, which was especially significant in the high-liquidity companies. (2) The increase of trade frequency could raise the liquidity of the high-liquidity and middle-liquidity companies. As to the low-liquidity companies, although the increase of trade frequency increased the liquidity, it raised their volatility and decreased their price finding speed. The main contributions of this paper¡¦s models are indicated as follows. Regarding a probability model of informed trade: first, it improves the prior ones by bringing the order-driven call market model; second, the addition of informed traders¡¦ possibility to use limit order in the model set-up better corresponds to the real market; third, the model can calculate the probability of informed trading of intraday trade section and thus can analyze the intraday and intraweek behavior or phenomenon of informed traders and the market; fourth, the model estimates the probability of informed trading using trade data, not order data, and thus avoids the probability of informed trade estimation error caused by order trade risk; fifth, the model calculates the probability of informed trade of individual stock after separating good and bad news and thus can analyze buy-sell informed trade behavior. Regarding the probability model of arbitrage trading, it provides a method to analyze whether self-stabilization mechanism-arbitrage trade exists in the market to investigate on the necessity of the stabilization fund and its intraday trade behavior. Finally, regarding the ratio empirical model of informed trading, since this paper calculated the section informed and uninformed trade ratio by simulating uninformed traders¡¦ intraday trade strategy and by extracting the ratio of the trade volume variation of intraday trade section explained by uninformed traders¡¦ intraday behavior variation using regression analysis, it can avoid the deficiency that every trade volume was regarded as from a single trader in the prior order empirical model of informed trading.

O objetivo principal deste trabalho é analisar o efeito da assimetria da informação no custo de capital próprio das empresas negociadas em bolsa de valores no Brasil. O tema está em constante debate sobre a existência dessa relação e até mesmo sobre sua relação com o custo de capital ser favorável ou não. A assimetria da informação foi estimada através da Probability of informed trading (PIN), mensurando de forma direta a existência de negociações com informação privilegiada para a confrontação com custo de capital das empresas brasileiras. O resultado encontrado não apresentou relação estatisticamente significante a 5% entre a PIN e o custo de capital, de forma que não foi possível verificar a relação entre assimetria da informação e o custo de capital. Adicionalmente, o coeficiente encontrado para a PIN no modelo adotado indica uma possível correlação negativa da variável estudada e o custo de capital, deste modo o estudo corrobora com a conclusão de Lambert et al. (2012), segundo a qual, em mercados líquidos, a assimetria da informação não exerce papel relevante e sim a quantidade e a qualidade da informação disponível, não importando a forma de entrada da informação no mercado. / The main objective of this thesis is to analyze the effect of information asymmetry on the cost of equity of companies traded in stock exchanges in Brazil. It is constantly debated whether this relationship exists and also whether information asymmetry\'s effect on the cost of equity is favorable or not. Information asymmetry has been estimated using the PIN (Probability of Informed Trading), directly measuring the existence of insider trading for confrontation with the cost of equity of Brazilian companies. The result obtained did not show a statistically significant relationship at the 5% level between the PIN and the cost of equity; therefore, it was not possible to ascertain the relationship between information asymmetry and cost of equity. Additionally, the coefficient found for the PIN on the selected model indicates a possible negative correlation between the studied variable and the cost of equity, which indicates that the study corroborates the conclusion of Lambert et al. (2012), according to which information asymmetry does not exert a significant role in liquid markets but rather this role is exerted by the quantity and quality of available information, regardless of how information reaches the market.

Defining ambiguity as investor's uncertainty about the precision of the observed information, Chapter One constructs an empirical measure of ambiguity based on analysts' earnings forecast information, and finds that the market tends to react more negatively to highly ambiguous bad news, while it tends to be less responsive to highly ambiguous good news. This result supports the theoretical argument of Epstein and Schneider (2003, 2008) that ambiguity-averse investors take a worst-case assessment of the information precision, when they are uncertain about the information precision. In addition, Chapter One shows that returns on stocks exposed to highly ambiguous and intangible information are more negatively skewed. Chapter Two finds that certain traders are informed about either the forthcoming analysts' forecasts or long-term value of the stock, and informed traders prefer to use medium-size trades to exploit their private information advantage. Specifically, medium-size trade imbalance prior to the forecast announcements is positively correlated with the nature of forecast revisions, while in the days immediately after the forecasts medium-size trade imbalance is positively correlated with future stock returns for up to four months. Small-size trade imbalance is also positively correlated with future returns but only following downward revisions. In contrast, it is also shown that large trades placed right after the forecasts are unprofitable and generate slightly negative profits in the long run. Overall, our results are consistent with the "stealth trading hypothesis" proposed by Barclay and Warner (1993).

本研究在探討家族、非家族控制企業與私有資訊交易之關係，私有資訊交易是以當未預期盈餘為負時，在每季盈餘宣告前之異常融券放空為判斷依據。我們希望了解家族控制企業相對於非家族控制企業是否存在較多之私有資訊交易。實證結果指出當未預期盈餘為負時，在每季盈餘宣告前，家族控制企業相較於非家族控制企業確實存在較多異常融券放空之現象。另外，我們從實證結果亦發現當未預期盈餘為負時，則家族成員涉入經營程度愈高、家族盈餘分配權愈低以及股份盈餘偏離程度愈高之公司，在每季盈餘宣告前，其融券放空之行為相對於其他企業會比較多，由此推論出家族控制特性與所有權結構和隱含資訊之融券放空行為有關。此外，研究結果亦指出巨量融券放空可以用來預測股票未來之異常報酬，但家族控制企業之巨量融券放空相對於非家族控制企業並沒有提供較多有用資訊來預測股票未來之超額報酬。 / We investigate the relation between the information content of short sales and organization structure. We want to know that informed trading occurs more readily in family-controlled firms than in nonfamily firms. Our analysis indicates that family-controlled firms experience substantially greater abnormal short sales prior to negative earnings shocks than nonfamily firms. The analysis also indicates that family-controlled firms sustain marginally less abnormal short sales prior to positive earnings surprises than nonfamily firms. Supplementary testing indicates that characteristics of family control and ownership intensify informed short selling. Further analysis suggests that high short-selling tend to be informative in predicting future returns. However, we find that high short-selling in family-controlled firms do not contains more useful information in forecasting stock returns than nonfamily firms.