Suits지수 구성요소를 이용한 조세 공평성 분석 = Measuring Tax Equity Using the Components of the Suits Index

다국어 초록 (Multilingual Abstract)

This study applies the method of income inequality decomposition in terms of the Gini coefficient into decomposing tax inequality in terms of the Suits index. Using the decomposition methodologies, the current study tests empirically whether changes in Korean corporate income tax system achieve or increase tax equity.
If the income recipients are classified into several groups according to their income, the Suits index is decomposed into the between-group, within-group and remaining components, and the changes in the value of the Suits index from pre-tax to post-tax income are also expressed as changes in the three components. The between-group component and its change are referred to vertical tax equity or pure tax progressivity with horizontal components. The within-group and remaining components and their changes are referred to horizontal tax equity.
If the vertical equity is achieved, the between-group component is not only positive and increasing in trend but its change is not also negative and decreasing in trend. If the horizontal equity is achieved, the within-group and residual components and their changes will be close to and converge to zero through time.
Based on the above hypotheses, this paper analyses 15 year data using graphs and the linear trend model to verify whether vertical and horizontal tax equities are achieved and increased through time. Testing is executed using univariate test, OLS regression, and bootstrap resampling method. As for the regression, the dependent variable is the change of year and the independent variables are the components or their changes in terms of the Suits index.
The results are summarized as follows.
First, the negative Suits index shows that the corporate income tax is regressive.
Second, the horizontal tax inequality measured by the within-group Suits index shows negative value and increasing trend through time because of the largest firm group.
Third, though income ranking changes after taxation show decreasing trend through time, its interpretation is marginal and restricted.

국문 초록 (Abstract)

본 연구는 Gini계수를 집단간, 집단내 및 잔여분 Gini계수의 세 가지 구성요소로 분해하고 조세의 소득 재분배 효과를 그 구성요소의 변화로 측정하는 소득 공평성 분석 방법론을 Suits지수에 응용하여 수평적 및 수직적 조세 공평성 분석을 수행하는 새로운 연구방법론을 제시하였다. 그리고 Suits지수의 구성요소를 분해하는 방법론을 이용하여, 조세 공평성 제고라는 법인세제의 정책 목표대로 수직적 및 수평적 조세 공평성이 각 연도에 달성되었는지 또한 장기적으로 향상 추세에 있는지를 실증적으로 밝혔다.
Suits지수 구성요소 또는 구성요소의 변화에 대한 단일변량분석 결과 및 이들을 독립변수로 한 선형추세모형을 이용한 OLS 회귀분석 및 Bootstrap 방법을 이용한 검정 결과를 요약하면 다음과 같다.
Suits지수와 그 구성요소는 평균적으로 음의 값으로서, 우리나라 법인세는 소득이 높은 기업이 낮은 기업보다 상대적으로 적은 조세를 부담하는 역진적 조세이다. 집단간 Suits지수가 특별한 추세를 보이지 않은 것과 달리, 집단내 Suits지수는 최근 연도에 가까울수록 불공평성이 더욱 심화되는 추세를 보였다. 집단내 Suits지수가 음의 값이고 악화되는 추세를 보이는 결과는 30-40대 대기업 때문에 발생한 대기업 효과이다. 과세로 인한 소득순위 변동은 감소 추세를 보였지만, 그 결과와 해석은 제한적이다.

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