The impact of Security Transaction Taxes (STTs) on the financial market has been studied by authors for decades, showing mixed results between positive, negative, or insignificant relations between STTs and financial volatility. This thesis adds a new approach to previous studies by taking an innovative long-term approach to the topic, analysing the effect of both the New York State STT (1905 – 1981) and the United States STT (1914 – 1966) on volatility in the New York Stock Exchange (NYSE) and NASDAQ as measured by the S&P500 Index. The period of investigation is from 1950 to 2019. This analysis reveals a negative relation between the NY STT and volatility when those are computed in long periods of time, implying that the presence (and increase) of STTs lead to a reduced volatility in the financial market. When breaking the analysis down into shorter periods of time the relationship between STTs and financial volatility proved to be insignificant. At the same time, the US STT is not statistically significant neither in the long-term nor in any of the separated shorter analysed periods. This thesis therefore highlights the relevancy of performing long-term studies rather than short-term ones which has been the focus of previous research.

Industrial revenue bonds (IRBs) possess special tax characteristics which provide an opportunity to test the interest tax shield hypothesis of Modigliani and Miller [1963]. The announcement day excess returns for IRB issues reflect a positive significant market reaction. However, this excess return is unrelated to the tax shield on the debt. Nor is it a function of non-debt tax shields, a proxy for an interior optimal capital structure, or the risk of the issue. It is consistent, however, with the argument that lRBs provide a subsidy to issuing firms. Miller's [1977] equilibrium model predicts that the tax rate of the marginal buyer of debt will be equal to the corporate tax rate. The Miller hypothesis is tested by comparing the yield spread between IRBs and taxable corporate debt. The empirical estimation indicates a segmentation of the market for tax-exempt debt. For short-term issues, the implied tax rate is not significantly different from the corporate tax rate, consistent with Miller’s prediction. For 1ong·term issues, the implied tax rate is significantly less than the corporate tax rate and decreases with maturity. This is consistent with the excess supply of tax-exempts being purchased by individuals in increasingly lower tax brackets. / Ph. D.