Labor Market Impact of Labor Cost Increase without Productivity Gain: A natural experiment from the 2003 social insurance premium reform in Japan

少子高齢化の進展に伴い、企業の社会保険料負担は年々大きくなっている。本稿では、社会保険料負担が雇用、労働時間、支払賃金に与える影響を分析する。日本の場合、社会保険料は原則、全国一律で設定されているため効果分析は難しいが、我々は、2003年の総報酬制導入を自然実験として利用することでその効果を測定した。その結果、社会保険料負担増は、雇用減少、平均労働時間の増加とそれに伴う平均年収の増加を引き起こした。雇用減少と平均年収増加が相殺し、企業の支払総賃金は変化しなかった。つまり、雇用継続された労働者は労働者負担分の社会保険料増加を労働時間増で賄い、その増加分は、雇用削減で企業は吸収した。企業負担分の社会保険料負担増加は企業が支払った。我々の分析結果は、生産性上昇を伴わない労働コスト増加は雇用を減らす可能性があることが示唆する。

Exploiting heterogeneous variations in labor cost increases due to Japan's 2003 social insurance premium reform as a natural experiment, we estimate the impacts of the increased social insurance premiums on employment, working hours, and payroll costs. Using the difference in differences (DID) method with establishment fixed effects, we find that firms reduce the number of employees and increase average annual earnings from longer working hours in response to an exogenous increase in labor costs without productivity gains. Firms manage to pay for this increase in the average wage paid to the remaining workers by reducing the number of employees to keep total payroll costs unchanged. In contrast, since social insurance premiums are shared equally between employees and employers, firms pay the remaining half of the premiums with which that they are imposed. Our results imply that an increase in labor costs without productivity gain may reduce employment.

Published: Kodama, Naomi, and Izumi Yokoyama, 2018. "The Labour market effects of increases in social insurance premium: Evidence from Japan," Oxford Bulletin of Economics and Statistics, Vol. 80(5), pp. 992-1019
https://onlinelibrary.wiley.com/doi/full/10.1111/obes.12226