增长指数债券和债务分配：太少，太贵？（英）

Growth-Indexed Bondsand Debt Distribution:Too Little, Too Costly? Julien Acalin WP/26/80 IMF Working Papersdescribe research inprogress by the author(s) and are published toelicit comments and to encourage debate.The views expressed in IMF Working Papers arethose of the author(s) and do not necessarilyrepresent the views of the IMF, its Executive Board,or IMF management. 2026APR IMF Working Paper Western Hemisphere Department Growth-Indexed Bonds and Debt Distribution: Too Little, Too Costly?*Prepared by Julien Acalin Authorized for distribution by Mai Chi DaoApril 2026 IMF Working Papersdescribe research in progress by the author(s) and are published to elicitcomments and to encourage debate.The views expressed in IMF Working Papers are those of theauthor(s) and do not necessarily represent the views of the IMF, its Executive Board, or IMF management. ABSTRACT:Sovereign state-contingent bonds have rarely been issued despite their theoretical debt-stabilization properties. This paper revisits this puzzle by analyzing when growth-indexed bonds are too limitedin scale, and when they are too costly, to materially improve debt sustainability. The results show that thebenefits of indexation are highly heterogeneous across countries. Under the realistic assumption that 20percent of the debt stock is indexed, reductions in the upper tail of the debt distribution are modest. Fullindexation yields more substantial improvements, especially when combined with an optimal loading on growth.Yet a sustained premium of 100 basis points would still offset most of the gains for many countries. Thesefindings suggest that the debt-stabilization properties of growth-indexed bonds would be limited, unless a large-scale and coordinated effort achieves both broad adoption and low issuance premia. Growth-Indexed Bonds and DebtDistribution: Too Little, TooCostly? Prepared by JulienAcalin 1Introduction Advanced economies have experienced large increases in their public debt-to-GDP ratiosover the past 15 years, driven in particular by the global financial crisis (GFC) and theCOVID-19 shock. The deep recession and slow economic recovery which followed the GFCraised concerns about debt sustainability in some countries, creating a vicious cycle: Nega-tive shocks on output and on public finances reduced debt sustainability, which translatedinto higher borrowing costs, thus worsening debt sustainability in those countries even more.To contain the impact of increasing borrowing costs, governments went through fiscal con-solidation, which acted as a drag on economic activity.These dynamics were particularlysalient in countries such as Spain and France, where the debt-to-GDP ratio rose, respectively,from 35 to 100 percent and from 64 to 92 percent between 2007 and 2013 (Figure 1). Although current debt levels may seem sustainable under baseline projections, negativeshocks to growth or interest rates could put debt ratios on an unsustainable path. Againstthis background, the issuance by sovereigns of debt instruments indexed to output—an ideaintroduced in its modern form by Shiller (1998) and further developed by Borensztein andMauro (2004)—has attracted renewed policy interest (Shiller et al., 2018). While sovereignstraditionally issue debt at fixed interest rates, growth-indexed bonds (GIBs) pay a time-varying coupon determined by a specific indexation formula. In its simplest form, the nominalindexed coupon rate at timet, denoted ¯it, is equal to the nominal growth rategtplus apredetermined contract termkt: wherektis known att−1 and ensures that an investor is indifferent between holding a GIBand a conventional plain-vanilla bond.1 The theoretical case for GIBs operates through two channels. First, by indexing couponpayments to growth, GIBs reduce the variability of the debt-to-GDP ratio and, therefore, thelikelihood of reaching dangerously high debt levels (Barr et al., 2014, Benford et al., 2016,Blanchard et al., 2016, Kim and Ostry, 2021, Pienkowski, 2017). Second, by making interestpayments procyclical, GIBs allow for more counter-cyclical fiscal policy during recessions,avoiding self-defeating consolidations (Borensztein and Mauro, 2004, Demertzis and Zenios,2019, Hatchondo and Martinez, 2012). Yet, if domestic residents hold such indexed bonds,their interest revenue will increase during good times and decrease during bad times. Thisprocyclicality in their income may reinforce, rather than smooth, the economic cycle. Notwithstanding their theoretical appeal, GIBs have rarely been issued in practice. Pastissuance has been limited in size and confined to debt-restructuring episodes (Costa Rica,Bulgaria, and Bosnia-Herzegovina in the 1980s and 1990s; Argentina in 2005, Greece in 2012,and Ukraine in 2015), and no sovereign has issued GDP-linked bonds with full symmetricrisk-sharing on a broad scale.2Two concerns feature prominently in the debate. First, moralhazard and data credibility: manipulation of official statistics