유효법인세율과 부채비율 사이의 인과관계 분석과 세법상 지급이자 손금불산입 규정의 유효성 평가

There have been many empirical studies investigating whether firms' characteristics affect their effective tax rates. As one of them, K.A. Jeon (1997) studied the determinants of the effective tax rates of Korean listed firms. The study obtained empirical results demonstrating that the effective tax rates are higher for firms with a higher debt ratio, and concluded that the reason for this is that the amount of interest expense that is not deducted in calculating tax to be paid is larger for firms with a higher debt ratio due to the tax provision for limiting the tax deductibility of interest expense. If this is the case, it implies that the tax provision does not satisfactorily achieve its originally intended effectiveness.By the way, firms will evidently try to avoid the tax disadvantages of the tax provision for limiting the tax deductibility of interest expense. Therefore, there may be another reason why the effective tax rates are higher for firms with a higher debt ratio. For example, it is also possible that higher effective tax rate causes higher debt ratio. That is, the causality between debt ratio and effective tax rate can be bi-directional.Taking this possibility into account, this study empirically tests the de facto causality between a debt ratio and an effective tax rate by performing the 2-stage least square regression analysis instead of the ordinary least square regression, and, based on test results, evaluates the actual effectiveness of the tax provision for limiting the tax deductibility of interest expense. The test results show that higher debt ratio causes higher effective tax rate, but the degree of this causality is not as strong as that presented in the existing literature. This means that the tax provision for limiting the tax deductibility of interest expense achieves its intended effectiveness considerably better than is implied by the existing literature.