研发分配不当是否导致了增长放缓？（英）

Did R&D MisallocationContribute to SlowerGrowth? Nils H. Lehr WP/25/183 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. 2025SEP IMF Working Paper Western HemisphereDepartment Did R&D Misallocation Contribute to Slower Growth?Prepared byNils H. Lehr Authorized for distribution byGustavo AdlerSeptember 2025 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:This paper provides evidence that rising misallocation in the R&D sector contributed to therecent slowdown in U.S. productivity growth. I develop a growth accounting framework allowing formisallocation of R&D resources across firms captured by wedges between their marginal cost and benefits ofR&D. I show that R&D wedges can be measured from R&D returns and document large and persistentdifferences in R&D returns across US-listed firms. Combining data and model, I estimate that frictions reducedproductivity growth by 18% over 1975–2014 and that rising misallocation in the R&D sector accounts for 25%of the growth slowdown. Did R&D Misallocation Contribute to Slower Growth?∗ Nils H. Lehr†IMF September 12, 2025 Abstract This paper provides evidence that rising misallocation in the R&D sector con-tributed to the recent slowdown in U.S. productivity growth.I develop a growthaccounting framework allowing for misallocation of R&D resources across firms cap-tured by wedges between their marginal cost and benefits of R&D. I show that R&Dwedges can be measured from R&D returns and document large and persistent differ-ences in R&D returns across US-listed firms. Combining data and model, I estimatethat frictions reduced productivity growth by 18% over 1975–2014 and that risingmisallocation in the R&D sector accounts for 25% of the growth slowdown. U.S. productivity growth has slowed down significantly in the last two decades. While totalfactor productivity (TFP) grew 0.5% per year in 1975–1995, its growth rate declined to0.3% in 2005–2018. Surprisingly, investment in research & development (R&D)—commonlyconsidered the driver of medium- and long-run productivity growth—has remained stableover the same time horizon.R&D expenditure amounted to 2.7% of GDP for 1975–95,compared to 2.9% for 2005–18. I provide evidence for an explanation of declining TFP growth at constant R&D invest-ment rooted in a simple decomposition. In endogenous growth models, productivity growthis the product of two terms: aggregate R&D investment and aggregate R&D productivity—the rate at which these investments are translated into growth. Slower growth despite stableR&D investment can then only be rationalized by declining aggregate R&D productivity. In turn, aggregate R&D productivity is a function of two forces:the average R&Dproductivity of firms and the efficiency with which R&D resources are allocated across them,orR&D Allocative Efficiency. A growing literature highlights the first channel and finds that“ideas are getting harder to find” (Bloom et al., 2020). Instead, this paper focuses on thesecond channel and provides evidence that declining allocative efficiency contributed to loweraggregate R&D productivity and, thus, economic growth. While some firms invest too muchin R&D relative to the inventions they produce, others do too little, and increasingly so.Quantitatively, this channel can account for 25% of the slowdown. Thus, not only are ideasgetting harder to find, but we are also increasingly looking for them in the wrong places. I reach these conclusions based on a growth accounting framework nesting workhorsegrowth models (Romer, 1990; Aghion and Howitt, 1992). Firms hire R&D workers to maxi-mize the private value created from innovation. I introduce frictions flexibly through exoge-nousR&D wedgesin their first-order conditions. These distort firms’ demand for R&D inputssuch that marginal returns on R&D are controlled by R&D wedges rather than equalizedacross firms. Growth occurs as a by-product of innovation, however, the private value cre-ated from an invention may not align perfectly with its contribution to productivity growth.I capture this divergence with animpact-value factorsuch that firms with low impact-valuefactor create a lot of private value, while contributing little to productivity growth. I show that the impact of private frictions, i.e.,R&D wedges, on the equilibrium economicgrowth rate is captured by a sufficient statistic, which I refer to asR&D Allocative Efficiency.When private and growth incentives are aligned, the baseline case in the literature, variationin R&D wedges