Estabilidade do coeficiente Beta e grau de governança corporativa. Um estudo com base em empresas brasileiras listadas na BM&FBOVESPA no período de setembro de 2005 a setembro de 2013

Abstract

The objective of this study is to establish a reverse relationship between Beta coefficient stability of portfolios and their levels of corporate governance. Risk is a subject that has been deeply studied since Markowitz (1952) published the article Portfolio Selection , and started what is called, The modern theory of finance . After this seminal article published by Markowitz, Sharpe (1964), Lintner (1965) and Mossin (1966) developed an extreme important pricing model called CAPM. To develop this model, the authors divided the risk in two different parts: the Beta Coefficient , a measure of the systematic risk, and the Specific Risk , a part of the risk that can be reduced through diversification. Besides that, the concept of corporate governance has been spread out as an important measure to benefit the investors, the company, the shareholders and the managers, bringing a reduction of the WACC, adding value to the all stakeholders. In order to structure this study, the stocks traded on BM&FBOVESPA were divided in four different portfolios in accordance to their different corporate governance level: Traditional (CTR), Level 1 (CN1), Level 2 (CN2) and Novo Mercado (CNM). The database was collected from September, 2005 through September 2013, and sectioned in eight periods of time, starting September of one year, ending September of the next one. Dummy variables were introduced on the database to evaluate the statistical significance, at 5% and 1% levels, of the changes on the Beta Coefficient of the portfolios. The results forced us to reject the hypothesis of establishing a reverse relation between Beta stability and corporate governance levels.