Resumen
This study verifies the contribution of a structural break (if any) to CAPM models. Therefore, we used all the assets listed in Bovespa and New York Stock Exchange in monthly frequencies. Three famous structural breaks tests were used. The results show that structural breaks are relevant in most models for most sectors of the economy. Then, the identified structural breaks are inserted in the models and the betas of CAPM models were re-estimated. The Betas that were statistically significant were chosen and their results compared to Market Beta for each sector of the economy. The results show that the estimated Betas resemble Market Beta in more than 78% of the economic sectors of the Brazilian and North-American markets.