A Study on Optimal Income Taxation with Welfare of Stigma and Rokyu

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K01711
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 07050:Public economics and labor economics-related
• Research Institution: Hokusei Gakuen University (2021-2022); Hokkaido University (2019-2020)
• Principal Investigator: Jun-ichi Itaya 北星学園大学, 経済学部, 教授 (20168305)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: スティグマ / 生活保護 / 不正受給者 / 漏給 / 統計的差別モデル / 納税者の怒りモデル

Outline of Final Research Achievements

Two theoretical models of stigma formation in welfare are developed by applying evolutionary game theory.
(1) In the dynamic statistical discrimination model, two long-run equilibria emerged. One equilibrium was that there were no unauthorized recipients, but no eligible recipients received benefits due to stigma (complete leakers). The other equilibrium was one in which some eligible recipients received benefits, but a large number of unauthorized recipients were created. (2)The dynamic taxpayer anger model shows that the only global equilibrium with both extremes is a mixed long-term equilibrium. In both equilibria, increasing benefits reduced the number of full leavers, but increased the number of unauthorized recipients. The most desirable policy outcome was an increase in the wage rate. The most desirable policy outcome was an increase in the wage rate, since an increase in the wage rate reduced both the number of full leakers and the number of unauthorized recipients.

Free Research Field

公共経済学

Academic Significance and Societal Importance of the Research Achievements

理論的な結論は、なるべく不正受給者および完全漏給者（資格があるのに受給しない人）を減少させるための最適な生活保護制度をデザインするための政策指針を得ることができた。しかし、統計的差別モデルを使うか、納税者の怒りモデルを使うかによって、到達可能な長期均衡点が異なる。しかし、両モデルはほぼ同じ政策的なインプリケーションを与えている。特に、賃金率の上昇が一番の望ましい政策であることが示されている。給付水準を上げることが次に望ましい。本研究から得られた政策的インプリケーションは、ある程度の一般性および普遍性があるので、現実の生活保護制度をデザインする際に適用できると考えられる。