介護報酬・自費サービス価格の「物価高連動」は成立するか ─ 連動対象・非対称性・負担配分の検討 ─ / Can "Inflation-Linked" Long-Term Care Fees and Private-Pay Service Prices Work? — Examining Index Targets, Asymmetry, and Burden Allocation —

要旨(Abstract) 日本語 SNS上で「せめて物価高に連動した報酬にしないと誰も浮かばれない」という主張がなされた。本稿はこの主張を出発点に、"介護報酬・自費サービス価格を物価に連動させる"という提案を分解し、その成立条件を検討する。「物価連動」は単一の政策ではなく、(a) 連動対象指標、(b) 連動係数の対称性(上昇時・下降時で同じ式を適用するか)、(c) 改定の頻度・タイミング、(d) 財源の帯(保険料・公費・利用者負担のいずれに反映するか)、(e) サービス種別間の一様性、という少なくとも5つの独立した制度設計変数の組み合わせであることを示す。 さらに、日本の社会保障制度には非対称スライドの実例(年金のマクロ経済スライド・物価スライド特例水準問題)と、物価高騰下でも報酬がサービス種別によって逆方向に動いた実例(令和6年度介護報酬改定における訪問介護基本報酬引き下げ)が既に存在することを一次資料で確認する。これらの実例を、公共支出理論(displacement effect)・労働経済学理論(名目賃金下方硬直性、COLA/エスカレーター条項の非対称設計)・福祉国家の政治学(blame avoidance)と接続し、「物価高→報酬増」という単純な対応関係が制度的にも政治的にも自明ではないことを論じる。ただし、物価高騰期と重なる時期に、自動連動とは異なる裁量的な経路(介護職員処遇改善支援補助金等)で事後的な処遇改善が行われた実例も確認し、現行制度が物価高に無反応なのではなく、反応の形式自体が指標連動的な自動ルールではなく政治的な意思決定に依存する、という二重の裁量性を持つことを示す。 加えて、順連動的な主張が業界当事者にとって個人の損得計算としては自己矛盾ではないという構造(集中した利益・分散したコスト、公共選択論)と、この構造がどれだけ「自分ゴト」として意識されるかが財源の可視化度・受益までの心理的距離によって業界内外で非対称になりうるという点(メンタルアカウンティング・心理的距離、行動経済学)を、補助的な検討として付す。本稿は、前作(志賀高史, 2026「職種間賃金比較の方法論的限界」)が確立した「比較対象の内生性」という論点を、政策運用そのものの非対称性という、もう一段上のレベルに拡張する続編として位置づけられる。 English A claim circulated on social media asserting that "at the very least, compensation should be indexed to price inflation, or no one will be able to keep their head above water." Taking this claim as its starting point, this paper decomposes the proposal to "index long-term care service fees and private-pay service prices to price changes" and examines the conditions under which it could hold. It shows that "price indexation" is not a single policy but a combination of at least five independent institutional design variables: (a) the target index, (b) the symmetry of the indexation coefficient (whether the same formula applies during both increases and decreases), (c) the frequency and timing of revisions, (d) the funding band (whether the effect falls on insurance premiums, public funds, or user co-payments), and (e) uniformity across service categories. The paper further confirms, using primary sources, that Japan's social security system already contains precedents of asymmetric indexation (the macroeconomic slide and the price-slide special exemption level in the public pension system) and of fee revisions moving in opposite directions across service categories even amid price inflation (the reduction of the base fee for home-visit care services in the fiscal year 2024 long-term care fee revision). These precedents are connected to public expenditure theory (the displacement effect), labor economics theory (downward nominal wage rigidity, the asymmetric design of COLA/escalator clauses), and welfare-state politics (blame avoidance), to argue that the simple correspondence "price increase → compensation increase" is neither institutionally nor politically self-evident. At the same time, the paper confirms an instance in which a discretionary channel distinct from automatic indexation (a subsidy for improving care workers' treatment) produced an ex post wage improvement during a period of price inflation, showing that the current system is not entirely unresponsive to price inflation but that the very form of its response depends on discretionary political decision-making rather than an automatic, index-linked rule — a double layer of discretion. In addition, the paper offers a supplementary examination of the structure under which a pro-indexation claim is not necessarily self-contradictory as an individual cost-benefit calculation for industry insiders (concentrated benefits and diffuse costs, from public choice theory), and of how the degree to which this structure is felt as "one's own concern" can be asymmetric between industry insiders and outsiders, depending on the visibility of the funding source and the psychological distance to the benefit (mental accounting and psychological distance, from behavioral economics). This paper is positioned as a sequel that extends the point established by the prior paper (Shiga, 2026, "Methodological Limits of Inter-Occupational Wage Comparisons") — the endogeneity of the comparison target — to a further, higher-level asymmetry: the asymmetry of policy operation itself.