A Study on Optimal Auditing Under the Living Wage System

생계급여하에서의 최적 소득조사

One of the main problems in Korea's public assistance program, the NBLS (National Basic Livelihood Security), is that the loophole of welfare system is continuously growing. Living wage program is the largest sub-program of the NBLS, and the most important determinant of amount of living wage for each beneficiary is the level of reported income. Therefore, accurate and effective income detection is essential in improving policy effects and furthermore reducing the leakage of wage expenditure as beneficiaries always have an incentive to underreport their income. Since most of them do not pay income tax, the welfare authority should exert an independent effort to effectively detect their income. Considering that living wage is a special kind of income tax of which marginal tax rate is -1, one can apply a classical theory of tax evasion to understand illegal or excessive receipt of living wage caused by income underreporting. Utilizing a classical theory given by Alingham and Sandmo (1972), this paper provides a theoretical analysis of the optimal income reporting of the beneficiary. Then an optimization problem is constructed from the government's viewpoint to derive optimal income detecting device (auditing). This paper proves that cut-off discriminated auditing outperforms random auditing and cut-off auditing which implies if the government assigns a positive audit probability to every reported income less than a certain level and the probability is inversely proportional to the level of reported income, it can minimize underreporting and then gradually reduce the leakage of wage expenditure.

본 논문은 전통적인 탈세이론 및 세무조사이론을 활용하여 우리나라 국민기초생활보장제도의 주요 정책수단인 생계급여하에서의 소득탈루(부정수급)와 정책당국 입장에서의 최적 소득조사전략에 대한 이론 분석을 시도하고, 이를 통해 소득파악 제고를 위한 정책적 시사점을 도출하는 것을 목적으로 한다. 생계급여의 누수는 최저생계비 부근의 소득자들을 중심으로 소득탈루가 집중됨으로써 발생하는데, 임의조사(random auditing), 차단조사(cut-off auditing), 차별조사 등의 소득조사전략별 비교분석을 통해, 일정 수준 이하의 신고소득에 대하여 신고소득 수준에 반비례하는 조사확률을 적용하는 차단식(cut-off) 차별조사전략을 적용하는 것이 소득파악률 제고 및 급여누수 최소화를 위해 가장 바람직함을 입증하였다.