Journal Article わが国の所得税の控除が所得格差是正に与える影響 : 配偶者控除見直しに関するマイクロ・シミュレーション分析
Effects of Deductions of Personal Income Tax on Income Inequality in Japan: A Microsimulation of Reform of Spousal Tax Deductions and Tax Credit

土居, 丈朗

68 ( 2 )  , pp.150 - 168 , 2017-04-26 , 岩波書店
本稿では,「平成29年度税制改正大綱」に盛り込まれた配偶者控除の見直しの影響や,わが国の所得税制において多用されている所得控除を税額控除化したときの所得格差是正効果を,マイクロ・シミュレーションの手法を用いて分析した.「日本家計パネル調査(JHPS)」の2014 年調査を用い,標本を「国勢調査」の世帯構成に合わせて比推定している.今般の配偶者控除の見直しが所得格差に与える影響は,ごくわずかであることが明らかとなった.これは,配偶者控除の見直しが,所得控除のまま行われたことも影響していると考えられる.そこで,所得控除の税額控除化が所得格差に与える影響を考察した.人的控除のみを税額控除化しただけでは,等価世帯可処分所得のジニ係数の低下は小さく,給与所得控除と公的年金等控除といった所得計算上の控除までも廃して,人的控除として税額控除を設けると,ジニ係数がさらに低下することが確認された.さらに,女性の働き方に中立的な税制にすべく,「130万円の壁」による手取りの逆転現象を解消するような「社会保険料割引(仮称)」を導入し,税額控除化に加えて行うとどうなるかを分析したところ,ジニ係数がこれまでより大きく低下した.社会保険料割引は,就業調整を意識せずに済む仕組みとして検討したものだが,所得格差是正にも効果があることが明らかとなった.
We investigate effects of reform of spousal tax deductions, which were listed in the 2017 tax reform outline, and deductions for persons on income inequality in Japan by using a microsimulation. The Japan Household Panel Survey(JHPS)in 2014 is used in the analyses. We find that the reform of exemptions for spouses does not substantially correct income disparity. It implies that the spousal tax deductions after the reform still remain as deductions from income(tax allowances), which have weaker effects in correcting income disparity relative to deductions from tax. In addition, we analyze a microsimulation which changes deducations from income to tax credits. That is, the reform in which deductions from income are abolished and tax credits based on household composition are newly established on only deductions for persons. We obtain the result that the Gini coefficient of the equivalent household disposable income slightly decreases. In order to decrease the Gini coefficient more, even deductions from earnings(deduction for employment income and deduction for public pensions)need to be abolished and tax credits need to be newly established. Moreover, according to a microsimulation, a “discount on social insurance premiums(tentative name),” which provides for partial compensation of premiums by using revenue from the personal income tax, acts to correct income inequality.

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