This paper describes and develops a trade off model of optimal capital structure by Bradley et al. (1984). The model is then tested to examine how changes in corporate tax rates affect the optimal capital structure of firms. Based on theoretical implications of the model, four hypotheses are derived stating that firms’ optimal debt-to-value ratio is (1) negatively related to financial distress costs, (2) negatively related to non-debt tax shields, (3) negatively related to firm volatility and (4) positively related to the corporate tax rate. Based on the results of two regression models applied on 753 Scandinavian and German firms, we find empirical support for hypothesis 1 and 3 while we find no empirical support for hypothesis 2 and 4. These results can be explained by problematic empirical proxies and in the light of the pecking-order theory.

This cumulative dissertation extends the literature strand on dynamic trade-off models in corporate finance. While Kane et al. (1984) and Fischer et al. (1989) have been probably first in developing dynamic trade-off models incorporating the effects of debt financing, it was Leland (1994) that really started the contingent claims revolution in corporate finance (Strebulaev and Whited, 2011, p. 25). Over the last 25 years, a whole strand of literature extended Leland's basic model to shed light on various financial decisions. To just provide some examples: Goldstein, Ju, and Leland (2001) based their model on a stochastic EBIT-process and allowed for an option to increase debt in order to understand the dynamic adjustment of capital structures. Strebulaev (2007) included external shocks into his capital structure models and gave indications on how capital structure tests shall be conducted. The contributions achieved in the essays of this dissertation focus on (i) more realistic conditions of default, (ii) an improved understanding of observed debt maturities and (iii) capital structures, (iv) the risk of applying the Equity IRR in financial decision making, as well as (v) the optimal choice between project financing and corporate financing.

This cumulative dissertation extends the literature strand on firm valuation and capital structure under distinctive fiscal considerations by elaborating on corporate finance issues that have not been resolved or not explained in their full magnitude. Essay one reassesses the appropriate valuation of a firm using the APV equation and more appropriately specifying one of its components, the value of tax savings. The second essay thematically follows essay one by utilizing the WACC approach in a multi-state setting under active debt policy. The third and final essay reconsiders capital structure under the artificial restriction of interest deductibility and its resulting influence on the value of potential tax savings. All essays incorporate loss distribution in default for either a partial or a complete loss scenario, thus providing additional insides on this crucial assumption in firm valuation under risky debt.

The share of corporate saving in total saving in South Africa has increased during the past four decades. In this dissertation various economic theories are examined in order to try to explain this change and to determine the possible implications of this change. The conclusion is that the relationship between the investment decision of companies and their savings decision is governed by the determinants of the financing choice of firms. These include cost, risk, control and availability. If, because of these factors, firms prefer to finance investment with retained earnings, there is a relationship between investment and the level of corporate saving. The degree to which the investment decision is dependent on the availability of internal financing will determine the importance of the level of corporate saving in a country. / Oor die afgelope vier dekades het die aandeel van maatskapybesparing in die totale besparing in Suid-Afika toegeneem. In hiersie vehandeling word veskillende ekonomiese teoriee ondersoek ten einde hierdie verandering te probeer veklaar en te probeer vasstel wat die implikasies van hierdie veandering is. Die gevolgtrekking waartoe gekom word, is dat die verband tussen die investeringsbeleid en die maatskappye se besparingsbesluit bepaal word deur faktore wat die finansieringskeuse van die firmas beinvloed, naamlik koste, risiko, beheer en beskikbaarheid. Indien hierdie faktore daartoe lei dat die maatskapye verkies om investering met terruggehoue bespaaring the finansier, is daar 'n verband tussen investering en die vlak van maatskappybesparing. Die mate waarin die investeringsbesluit afhanklik is van die beskikbaarheid van interne finansiering, sal bepaal hoe belangrik die vlak van maatskappybesparing in 'n land is. / Economics and Management Sciences / M.Com.

本論文包含二篇與公司財務相關之文章，第一篇文章嘗試在考量總體經濟條件和公司生產力衝擊下，建構一個簡單結構式模型以探討公司之資本結構決策。特別的是，由該模型可得到公司最適負債比率與總體經濟條件衝擊之報酬波動性呈反向關係，惟公司最適負債比率與公司生產力衝擊之報酬波動性呈正向關係。第二篇文章係利用對稱寡占產業均衡模型，以探討產業內經理人薪酬決策之異質性。即使產業內所有公司皆為同質，在模型均衡下存在有些公司會採取激勵性薪酬，而其他公司則不採取激勵性薪酬。該模型預期當市場競爭性增加時，產業內公司經理人薪酬決策會更具異質性。此外，上述二篇文章皆分別以美國製造業資料進行實證，並且實證結果均符合其模型之預期。 / This dissertation proposes two essays about corporate finance. Essay one develops a simple structural model to investigate a firm’s capital structure choices in consideration of macroeconomic conditions and firm-level productivity shocks. The model particularly generates the implication that the optimal debt ratio is negatively correlated to the return volatility of macroeconomic conditions, but positively correlated to that of firm-level productivity. Essay two is contributed to explore the heterogeneity of the compensation decision within the industry by employing a symmetric oligopoly industry equilibrium model. Within the equilibrium some firms will adopt incentive pay while others will not, even though all firms are ex ante identical. The model predicts that there is more heterogeneity in the compensation decision as the intensity of market competition increases. Both of the two essays further provide empirical evidence of the US manufacturing industry to support the model implications.

本文建立一公司稅、累進個人稅、非債稅盾和破產可能之不確定經濟模型，探討公司的投資理財決策行為。和以前文獻最大的不同點，在於公司風險債利率水準明顯且完全的內生化處理，此內生化利率不僅受公司舉債額度的財務決策影響，也會反應公司現行投資或資本存量的實質決策，模型中的財務和實質決策具有完全互動之特性。 累進個人稅下，只要存在一組投資人間的邊際稅率結構，能排除套稅資產配置，則市場無套稅價格和競爭均衡便存在。此一結果，使本文模型中的資產評價得以建立於競爭財務市場均衡的基礎。市場均衡下，公司債利率會隨公司舉債額度而同向、投資額度而反向調整，此時股東與債權人間的代理成本問題完全消失、市場具有公平保護債權人的機能。如果公司債利率外生而無法依市場均衡評價，則由於代理成本問題存在，使公司最適投資相對低於、舉債額度則高於利率內生之最適水準。另外，傳統一些稅制分析法的資本結構決定理論，只是本文之特例。 稅盾變化，如投資減免率或定額減免等，對公司最適投資和舉債的影響，除以前文獻之結果外，還包含一利率回饋效果，後者可能改變以前文獻之結論。例如，本文發現獎勵投資之折舊率或投資扣抵的政策美意，可能反而造成抑制投資的結果，本文這部分之結論，或可提供有關公司資本結構決定之實證研究新的詮釋，另外在稅制設計上亦具政策上的含意。

The share of corporate saving in total saving in South Africa has increased during the past four decades. In this dissertation various economic theories are examined in order to try to explain this change and to determine the possible implications of this change. The conclusion is that the relationship between the investment decision of companies and their savings decision is governed by the determinants of the financing choice of firms. These include cost, risk, control and availability. If, because of these factors, firms prefer to finance investment with retained earnings, there is a relationship between investment and the level of corporate saving. The degree to which the investment decision is dependent on the availability of internal financing will determine the importance of the level of corporate saving in a country. / Oor die afgelope vier dekades het die aandeel van maatskapybesparing in die totale besparing in Suid-Afika toegeneem. In hiersie vehandeling word veskillende ekonomiese teoriee ondersoek ten einde hierdie verandering te probeer veklaar en te probeer vasstel wat die implikasies van hierdie veandering is. Die gevolgtrekking waartoe gekom word, is dat die verband tussen die investeringsbeleid en die maatskappye se besparingsbesluit bepaal word deur faktore wat die finansieringskeuse van die firmas beinvloed, naamlik koste, risiko, beheer en beskikbaarheid. Indien hierdie faktore daartoe lei dat die maatskapye verkies om investering met terruggehoue bespaaring the finansier, is daar 'n verband tussen investering en die vlak van maatskappybesparing. Die mate waarin die investeringsbesluit afhanklik is van die beskikbaarheid van interne finansiering, sal bepaal hoe belangrik die vlak van maatskappybesparing in 'n land is. / Economics and Management Sciences / M.Com.