職種間賃金比較の方法論的限界 ― 処遇改善政策と内部公平性理論からの検討 ― 「介護職の給料は理学療法士を超えるか」という予測命題の条件分析 ─ / Methodological Limits of Inter-Occupational Wage Comparisons —Institutional Limits of Wage-Improvement Policies and the Endogeneity of Wage Reference Groups — A Conditional Analysis of the Prediction That Caregiver Wages Will Overtake Physical Therapist Wages —

要旨(Abstract) 日本語 SNS上で「介護職の給料が理学療法士を超える日が来る」という主張が、国による処遇改善の強化を根拠として提示された。この主張に対し、原資(財源)についての疑問が投げかけられたところ、発信者からは「原資を税金や保険料だけでは考えていません」という応答があった。その応答により、当初の論拠(国の処遇改善)に加えて、税・保険料以外の財源も含む前提が示された。ただし、その財源の内容や配分原理は本文上明示されていない。 本稿はこの一連のやり取りを出発点に、 「介護職の賃金が理学療法士の賃金を恒常的に超える」という予測命題が成立するために必要な条件を、二つの独立した観点から検討する。第一に、制度分析の観点から、介護報酬と診療報酬が別々の審議機関(社会保障審議会介護給付費分科会・中央社会保険医療協議会)によって決定される構造を確認し、処遇改善加算(2024年6月に旧3加算を一本化した「介護職員等処遇改善加算」 )が資格不問の制度であること、また加算率の強化が診療報酬側の水準に直接作用する制度的経路を持たないことを、告示・通知の一次資料に基づいて示す。第二に、労働経済学理論の観点から、比較対象となる職種(理学療法士)が賃金差の縮小に対して無反応であるという暗黙の前提(ceteris paribus)が、公平性理論(equity theory)およびleapfrogging型賃金交渉モデルに照らして成立しにくいことを論じる。 両観点は独立に、同一の結論――当該予測を一般的・恒常的な命題として支持することは説明不足のままでは困難である――を支持する。本稿はまた、比較の前提として「比較粒度(自法人内/地域内/地方単位/全国平均)」と「比較対象選択の妥当性」という二つの論点が、元の主張においては明示されていないことも指摘する。これらの論点は、SNS上の短い主張が、政策・市場・経営判断という異なるレベルの因果メカニズムを一本の線でつなぎがちであることを示す一例として位置づけられる。 English A claim circulated on social media asserting that “the day may come when caregivers’ wages overtake those of physical therapists, ”citing the government’s strengthening ofwage-improvement measures for care workers as its basis. When questioned about the funding source for this prediction, the original poster responded that “the funding isnot limited to taxes and insurance premiums.” This response introduced a premise that funding sources other than taxes and insurance premiums were also being considered, in addition to the original justification of government-led wage improvement. However, the content of those additional funding sources and the principle by which they would be allocated were not specified in the text. Taking this exchange as its starting point, this paper examines the conditions under which the prediction “caregiver wages will permanently overtake physical therapist wages” could hold, from two independent perspectives. First, from an institutional- analysis perspective, the paper confirms that long-term care service fees and medical service fees are determined by separate deliberative bodies (the Long-Term Care Benefit Costs Subcommittee of the Social Security Council, and the Central Social Insurance Medical Council), and shows, based on primary-source notifications and public notices, that the Wage-Improvement Subsidy for Care Workers (unified into a single subsidy scheme in June 2024) applies regardless of formal qualification, and that no confirmed institutional pathway directly links its subsidy rate to the fee levels determined on the medical-service-fee side that underlie physical therapists’ compensation. Second, from a labor-economics-theory perspective, the paper argues that the implicit c et eri s p ari b us assumption — that the reference occupation (physical therapists) will not react to a narrowing wage gap — is difficult to sustain in light of equity theory and leapfrogging-style wage bargaining models. Both perspectives independently support the same conclusion: without additional explanation, the prediction cannot be supported as a general, permanent proposition. The paper further points out that two prerequisite issues — the granularity of comparison (within a single organization, regional, prefectural/local, or national average) and the validity of the chosen reference occupation — are left unspecified in the original claim. These issues are presented as an illustrative case of how short social-media claims tend to conflate causal mechanisms operating at distinct levels — policy, market, and managerial decision-making — into a single line of reasoning.