Category Archives: Research

“Austerity,” EJ, 2021

Economic Journal, February 2021, with Harris Dellas. PDF.

We study the optimal debt and investment decisions of a sovereign with private information. The separating equilibrium is characterised by a cap on the current account. A sovereign repays debt amount due that exceeds default costs in order to signal creditworthiness and smooth consumption. Accepting funding conditional on investment/reforms relaxes borrowing constraints, even when investment does not create collateral, but it depresses current consumption. The model contains the signalling elements emphasised by creditors in the Greek austerity programmes and is consistent with the reduction in the loans issued by Greece and their interest rate following the 2015 election.

“Money Creation, Bank Profits, and CBDC,” VoxEU, 2021

VoxEU, February 5, 2021. HTML.

Based on CEPR DP 15457, I assess possible implications of the introduction of retail CBDC for bank profits. The model implies annual implicit subsidies to U.S. banks of up to 0.8 percent of GDP during the period 1999-2017.

Comments on Geneva Report 23

Panel with Elga Bartsch, Agnès Bénassy-Quéré, Giancarlo Corsetti, Olivier Garnier, and Charles Wyplosz. Moderated by Tobias Broer.

Elga Bartsch, Agnès Bénassy-Quéré, Giancarlo Corsetti, Xavier Debrun: Geneva Report 23 | It’s All in the Mix: How Monetary and Fiscal policies Can Work or Fail Together.

Event at PSE.

My comments on the report.

“The Pandemic Endgame,” VoxEU, 2021

VoxEU, January 11, 2021, with Martin Gonzalez-Eiras. HTML.

Based on the CEPR discussion paper, we draw conclusions for the pandemic endgame. We explain why Israel will likely impose a harsher lockdown than other countries, especially poor ones. And why we should expect “inverse lockdowns”—measures to stimulate social interaction.

Reading List on ‘Free’ or ‘Not-so-free’ Public Debt

Risk, Discounting, and Dynamic Efficiency

In the presence of risk, a comparison of the risk-free interest rate and the expected growth rate is insufficient to assess whether an economy is dynamically efficient or inefficient. Stochastic discount factors—not risk-free interest rates—enter the government’s budget constraint, even if debt is safe.

These points are made, for example, by Andrew Abel, N. Gregory Mankiw, Lawrence Summers, and Richard Zeckhauser (Assessing Dynamic Efficiency: Theory and Evidence, REStud 56(1), 1989),

the issue of dynamic efficiency can be resolved by comparing the level of investment with the cash flows generated by production after the payment of wages … dynamic efficiency cannot be assessed by comparing the safe rate of interest and the average growth rate of the capital stock, output, or any other accounting aggregate,

or Henning Bohn (The Sustainability of Budget Deficits in a Stochastic Economy, JMCB 27(1), 1995),

discounting at the safe interest rate is usually incorrect. … popular fiscal policy “indicators” like deficit levels or debt-GNP ratios may provide very little information about sustainability. … the intertemporal budget constraint imposes very few restrictions on the average primary balance.

Recent work in which these themes appear include papers by Zhengyang Jiang, Hanno Lustig, Stijn Van Nieuwerburgh, and Mindy Xiaolan (Manufacturing Risk-free Government Debt, NBER wp 27786, 2020), Robert Barro (r Minus g, NBER wp 28002, 2020), or Stan Olijslagers, Nander de Vette, and Sweder van Wijnbergen (Debt Sustainability when r−g<0: No Free Lunch after All, CEPR dp 15478, 2020).

Intergenerational Risk Sharing

With overlapping generations the way the government manages its debt has implications for intergenerational risk sharing, see for example Henning Bohn (Risk Sharing in a Stochastic Overlapping Generations Economy, mimeo, 1998), Robert Shiller (Social Security and Institutions for Intergenerational, Intragenerational, and International Risk Sharing, Carnegie-Rochester Conference on Public Policy 50, 1999), or Gabrielle Demange (On Optimality of Intergenerational Risk Sharing, Economic Theory 20(1), 2002).

Long-Run Debt Dynamics and Fiscal Space

Dmitriy Sergeyev and Neil Mehrotra (Debt Sustainability in a Low Interest World, CEPR dp 15282, 2020) offer an analysis of long-run debt dynamics under the assumption that the primary surplus systematically, and strongly responds to the debt-to-GDP ratio such that the government’s intertemporal budget constraint is necessarily satisfied:

Population growth and productivity growth have opposing effects on the debt-to-GDP ratio due to their opposing effects on the real interest rate. Lower population growth leaves the borrowing rate unchanged while directly lowering output growth, shifting the average debt-to-GDP ratio higher. By contrast, when the elasticity of intertemporal substitution is less than one, a decline in productivity growth has a more than a one-for-one effect on the real interest rate, lowering the cost of servicing the debt and thereby reducing the average debt-to-GDP ratio. To the extent that higher uncertainty accounts for low real interest rates, we find that
the variance of the log debt-to-GDP ratio unambiguously increases with higher output
uncertainty. However, uncertainty also has an effect on the mean debt-to-GDP ratio that
depends on the coefficient of relative risk aversion. Higher uncertainty lowers the real
interest rate but this effect may be outweighed by an Ito’s lemma term due to Jensen’s
inequality that works in the opposite direction.

Sergeyev and Mehrotra also consider the effects of rare disasters as well as of a maximum primary surplus which implies that debt becomes defaultable and the interest rate on debt features an endogenous risk premium, generating the possibility of a “tipping point” with a slow moving debt crises as in Guido Lorenzoni and Ivan Werning (Slow Moving Debt Crises, AER 109(9), 2019).

Ricardo Reis (The Constraint on Public Debt when r<g But g<m, mimeo, 2020) analyzes a non-stochastic framework under the assumption that the marginal product of capital, m, exceeds the growth rate, g, which in turn exceeds the risk-free interest rate, r. Reis considers the case where m is the relevant discount rate, for example because r features a liquidity premium:

there is still a meaningful government budget constraint once future surpluses and debt are discounted by the marginal product of capital.

He shows the following:

  • The debt due to a one-time primary deficit can be rolled over indefinitely and disappears asymptotically as long as r<g.
  • With permanent primary deficits that grow at the same rate as debt and output, the government’s intertemporal budget constraint features a bubble component due to r<m. This corresponds to the usual seignorage revenue measure (see p. 173 in Niepelt, Macroeconomic Analysis, 2019).
  • Suppose that from tomorrow on, the primary deficit and debt quotas are given by d and b, respectively. Then, the present value of total net revenues in the government’s budget constraint equals [- d + (m – r)*b] / (m-g). Both m>g and g>r relax the constraint, as does a lower r.
  • Along a balanced growth path, b = [- d + (m – r)*b] / (m-g) and thus, d = (g-r)*b where d is assumed to be positive. Reis argues that b cannot be larger than total assets relative to GDP. Accordingly, the deficit cannot exceed total assets times (g-r).

Reis concludes that most of the bubble component “has already been used.” In addition to developing a model that yields m>g>r in equilibrium he also discusses the role of inflation (stable inflation generates fiscal space because it renders debt safer and thus increases demand for debt) and inequality (more inequality increases fiscal space).

Blanchard’s Presidential Address

In his presidential address, Olivier Blanchard (Public Debt and Low Interest Rates, AER 109(4), 2019) argues that the risk-free interest rate has fallen short of average US growth rate (and similarly, in other countries). Importantly—and implicitly addressing Abel, Mankiw, Summers, Zeckhauser, and Bohn (see above)—he also argues that risk is not that much of an issue as far as the sustainability of public debt is concerned:

Jensen’s inequality is thus not an issue here. In short, if we assume that the future will be like the past (admittedly a big if), debt rollovers appear feasible. While the debt ratio may increase for some time due to adverse shocks to growth or positive shocks to the interest rate, it will eventually decrease over time. In other words, higher debt may not imply a higher fiscal cost.

Most of his formal analysis doesn’t focus on debt though. Instead he analyzes the effects of risk-free social security transfers from young to old in a stochastic OLG economy. (There are close parallels between debt and such transfers to the old that are financed by contemporaneous taxes on the young.) In a steady-state with very low interest rates higher transfers have two effects on welfare, by (i) providing an attractive substitute for savings and by (ii) reducing capital accumulation and thereby lowering wages and raising the interest rate. If the economy initially is dynamically inefficient both effects are welfare improving because (i) capital accumulation with a low return is replaced by higher yielding intergenerational transfers and (ii) lower wages and higher interest rates are attractive, starting from a situation with a low interest rate. In a stochastic economy the first channel yields welfare gains as long as the growth rate exceeds the risk-free rate, and the second channel yields welfare gains (approximately) when the growth rate exceeds the marginal product of capital. Blanchard argues

[b]e this as it may, the analysis suggests that the welfare effects of a transfer may not necessarily be adverse, or, if adverse, may not be very large.

In the corresponding case with debt there is another effect because the intergenerational transfer is not risk-free; the size of this additional effect depends on the path of the risk-free interest rates (Blanchard assumes that the debt level is stabilized which requires net tax payments by the young to reflect the contemporaneous risk-free rate). In the slightly different case where debt is increased once and then rolled over, without adjusting taxes in the future, the sustainability and welfare implications are ambiguous and critically depend on the production function:

In the linear case, debt rollovers typically do not fail [my emphasis] and welfare is increased throughout. For the generation receiving the initial transfer associated with debt issuance, the effect is clearly positive and large. For later generations, while they are, at the margin, indifferent between holding safe debt or risky capital, the inframarginal gains (from a less risky portfolio) imply slightly larger utility. But the welfare gain is small … . In the Cobb-Douglas case however, this positive effect is more than offset by the price effect, and while welfare still goes up for the first generation (by 2 percent), it is typically negative thereafter. In the case of successful debt rollovers, the average adverse welfare cost decreases as debt decreases over time. In the case of unsuccessful rollovers, the adjustment implies a larger welfare loss when it happens. If we take the Cobb-Douglas example to be more representative, are these Ponzi gambles, as Ball, Elmendorf, and Mankiw (1998) have called them, worth it from a welfare viewpoint? This clearly depends on the relative weight the policymaker puts on the utility of different generations [my emphasis].

Blanchard argues that the marginal product of capital may be smaller than commonly assumed, implying that it is more likely that the welfare effects working through (ii) are positive (those working through (i) are very likely positive). Finally, he also presents some additional potential arguments pro and con higher public debt.

Blanchard’s work has attracted substantial criticism, for instance at the January 2020 ASSA meetings (see this previous post). In a short paper presented at the meetings, Johannes Brumm, Laurence Kotlikoff, and Felix Kubler (Leveraging Posterity’s Prosperity?) point out that a negative difference between average interest and growth rates is not necessarily indicative of dynamic inefficiency (see the discussion above) and that Blanchard’s analysis disregards tax distortions as well as the welfare effects from intergenerational risk sharing (again, see above):

To see the distinction between risk-sharing and a Ponzi scheme, modify B’s two-period model to include agents working when old if they don’t randomly become disabled. Now workers face second-period asset income and labor earnings risk. The government has no safe asset in which to invest. If it borrows, invests in capital, and taxes bond holders its excess return, “safe” debt is identical to risky capital. But if the net taxes are only levied on the non-disabled, bonds become a valued risk-mitigating asset and their return can be driven far below zero. This scheme could be, and to some extend it is, implemented through progressive taxation. If, observing this gap between growth and safe rates, the government decides to institute an “efficient” Ponzi scheme with a fixed pension benefit financed on a pay-go basis by taxes on workers, net wages when young will be more variable, raising generation-specific risk and potentially producing an outcome in which no generation is better off and at least one is worse off.

Brumm, Kotlikoff, and Kubler also note that the effective interest rate at which US households are borrowing is much higher than the borrowing rate of the government; this undermines Blanchard’s approach to gauge the welfare implications. And they point out that the scheme suggested by Blanchard could harm other countries by reducing global investment.

Jasmina Hasanhodzic (Simulating the Blanchard Conjecture in a Multi-Period Life-Cycle Model) simulates a richer OLG model and rejects the Blanchard conjecture of Pareto gains due to higher transfers:

It shows that the safe rate on government debt can, on average, be far less than the economy’s growth rate without its implying that ongoing redistribution from the young to the old is Pareto improving. Indeed, in a 10-period, OLG, CGE model, whose average safe rate averages negative 2 percent on an annual basis, welfare losses to future generations resulting from the introduction of pay-go Social Security, financed with a 15 percent payroll tax, are enormous—roughly 20 percent measured as a compensating variation relative to no policy.

Relative to Blanchard’s simulations, her model implies more negative consequences of crowding out on wages, a higher tax burden from the transfer scheme, and more induced old-age consumption risk.

Michael Boskin (How, When and Why Deficits Are Dangerous) offers a broad discussion of potential weaknesses of Blanchard’s analysis. Richard Evens (Public Debt, Interest Rates, and Negative Shocks) questions Blanchard’s simulations on calibration grounds and notes that he couldn’t replicate some of Blanchard’s findings.

On his blog, John Cochrane argues along similar lines as Ricardo Reis: Even if r<g, expected primary deficits are so large that debt quotas will explode nevertheless.

Olivier Blanchard on Markus’ Academy.

Note: This post was updated several times.

John Cochrane about CBDC and Me

Writing about CBDC, John Cochrane makes it clear that he is in favor. He links to my work and writes

Dirk Niepelt has written a lot about CBDC theory, including reserves for all in 2015, a recent Vox-EU summary and papers,  here with Markus Brunnermeier a JME paper “CBDC coupled with central bank pass-through funding need not imply a credit crunch nor undermine financial stability,” a follow up including “The model implies annual implicit subsidies to U.S. banks of up to 0.8 percent of GDP during the period 1999-2017.”  Here  “reserves for all” “does not affect macroeconomic outcomes,”

Not Much Left of “Modern Monetary Theory”

Alberto Bisin (Journal of Economic Literature, December 2020) reviews Stephanie Kelton’s “The Deficit Myth: Modern Monetary Theory and the Birth of the People’s Economy:”

Never is its logical structure expressed in a direct, clear way, from head to toe. … Some of these statements are literally correct but used for incorrect or misleading implications—plays on words, effectively. They seem taken directly from the book of tricks of the Greek sophists (the ones Aristophanes makes fun of).

John Cochrane (blog post, July 2020) reviews the same book:

Skeptics have called it “magical monetary theory.” They’re right.

Dirk Niepelt (blog post/Neue Zürcher Zeitung (in German), April 2019):

The Macroeconomic Perpetuum Mobile.

“Optimally Controlling an Epidemic,” CEPR, 2020

CEPR Discussion Paper 15541, December 2020, with Martin Gonzalez-Eiras. PDF (local copy).

We propose a flexible model of infectious dynamics with a single endogenous state variable and economic choices. We characterize equilibrium, optimal outcomes, static and dynamic externalities, and prove the following: (i) A lockdown generically is followed by policies to stimulate activity. (ii) Re-infection risk lowers the activity level chosen by the government early on and, for small static externalities, implies too cautious equilibrium steady-state activity. (iii) When a cure arrives deterministically, optimal policy is dis-continous, featuring a light/strict lockdown when the arrival date exceeds/falls short of a specific value. Calibrated to the ongoing COVID-19 pandemic the baseline model and a battery of robustness checks and extensions imply (iv) lockdowns for 3-4 months, with activity reductions by 25-40 percent, and (v) substantial welfare gains from optimal policy unless the government lacks instruments to stimulate activity after a lockdown.

The Economist on CBDC and Disintermediation

The Economist discusses the risk of CBDC-induced bank disintermediation. Their summary of the 2019 paper by Markus Brunnermeier and myself:

If people prefer CBDCS, however, the central bank could in effect pass their funds on to banks by lending to them at its policy interest rate. “The issuance of CBDC would simply render the central bank’s implicit lender-of-last-resort guarantee explicit,” wrote Markus Brunnermeier of Princeton University and Dirk Niepelt of Study Centre Gerzensee in a paper in 2019. Explicit and, perhaps, in constant use.

“CBDC: State of Play, Practical Challenges, Open Issues,” SUERF Webinar, 2020

SUERF Webinar “CBDC: State of play, practical challenges, open issues” with Ulrich Bindseil (ECB) and Morten Bech (BIS). Moderated by Dirk Niepelt. December 4, 2020, 2 pm.

“Monetary Policy with Reserves and CBDC: Optimality, Equivalence, and Politics,” CEPR, 2020

CEPR Discussion Paper 15457, November 2020. PDF (local copy).

We analyze policy in a two-tiered monetary system. Noncompetitive banks issue deposits while the central bank issues reserves and a retail CBDC. Monies differ with respect to operating costs and liquidity. We map the framework into a baseline business cycle model with “pseudo wedges” and derive optimal policy rules: Spreads satisfy modified Friedman rules and deposits must be taxed or subsidized. We generalize the Brunnermeier and Niepelt (2019) result on the macro irrelevance of CBDC but show that a deposit based payment system requires higher taxes. The model implies annual implicit subsidies to U.S. banks of up to 0.8 percent of GDP during the period 1999-2017.

“Dynamic Tax Externalities and the U.S. Fiscal Transformation,” JME, 2020

Journal of Monetary Economics, with Martin Gonzalez-Eiras. PDF. (Appendix: PDF.)

We propose a theory of tax centralization in politico-economic equilibrium. Taxation has dynamic general equilibrium implications which are internalized at the federal, but not at the regional level. The political support for taxation therefore differs across levels of government. Complementarities on the spending side decouple the equilibrium composition of spending and taxation and create a role for inter governmental grants. The model provides an explanation for the centralization of revenue, introduction of grants, and expansion of federal income taxation in the U.S. around the time of the New Deal. Quantitatively, it accounts for approximately 30% of the federal revenue share’s doubling in the 1930s, and for the long-term increase in federal grants.

“Austerity,” EJ, forthcoming

Economic Journal, forthcoming, with Harris Dellas. PDF.

We study the optimal debt and investment decisions of a sovereign with private information. The separating equilibrium is characterized by a cap on the current account. A sovereign repays debt amount due that exceeds default costs in order to signal creditworthiness and smooth consumption. Accepting funding conditional on investment/reforms relaxes borrowing constraints, even when investment does not create collateral, but it depresses current consumption. The model contains the signalling elements emphasized by creditors in the Greek austerity programs and is consistent with the reduction in the loans issued by Greece and their interest rate following the 2015 election.

“Digital Money, Payments and Banks,” CEPR/IESE Report, 2020

Discussion of Antonio Fatás’ chapter in Elena Carletti, Stijn Claessens, Antonio Fatás, Xavier Vives, The Bank Business Model in the Post-Covid-19 World, CEPR/IESE report, London, June 2020. PDF.

Antonio’s chapter offers a rich overview of the dramatic changes in the world of money and banking that we have seen in recent years. I focus on two themes: the nature of money and how it relates to these developments, and the government’s response to the structural changes we observe.

I discuss the price of money, its fundamental value, store-of-value bubble, and liquidity bubble components; the opaque legal tender concept and the absurd situation that governments outlaw the use of government money (contrary to what some theories would imply); the role of trust in a world without cash; and the substitution of money by smart contracts tied to a database.

And I comment on the many facets of digitalization; the time lag between the origination of new business models and regulatory catch-up; and on central bank digital currency as a key element of structural change in the financial system.

“Reserves For All? Central Bank Digital Currency, Deposits, and their (Non)-Equivalence,” IJCB, 2020

International Journal of Central Banking. PDF.

This paper offers a macroeconomic perspective on the “Reserves for All” (RFA) proposal to let the general public hold electronic central bank money and transact with it. I propose an equivalence result according to which a marginal substitution of outside money (e.g., RFA) for inside money (e.g., deposits) does not affect macroeconomic outcomes. I identify key conditions for equivalence and argue that these conditions likely are violated, implying that RFA would change macroeconomic outcomes. I also relate the analysis to common arguments found in discussions on RFA and point to inconsistencies and open questions.

“Tractable Epidemiological Models for Economic Analysis,” CEPR, 2020

CEPR Discussion Paper 14791, May 2020, with Martin Gonzalez-Eiras. PDF (local copy).

We contrast the canonical epidemiological SIR model due to Kermack and McKendrick (1927) with more tractable alternatives that offer similar degrees of “realism” and flexibility. We provide results connecting the different models which can be exploited for calibration purposes. We use the expected spread of COVID-19 in the United States to exemplify our results.

“On the Optimal ‘Lockdown’ during an Epidemic,” CovEc, 2020

Covid Economics, April 2020, with Martin Gonzalez-Eiras. PDF.

We embed a lockdown choice in a simplified epidemiological model and derive formulas for the optimal lockdown intensity and duration. The optimal policy reflects the rate of time preference, epidemiological factors, the hazard rate of vaccine discovery, learning effects in the health care sector, and the severity of output losses due to a lockdown. In our baseline specification a Covid-19 shock as currently experienced by the US optimally triggers a reduction in economic activity by two thirds, for about 50 days, or approximately 9.5 percent of annual GDP.

“On the Optimal ‘Lockdown’ during an Epidemic,” CEPR, 2020

CEPR Discussion Paper 14612, April 2020, with Martin Gonzalez-Eiras. PDF (local copy).

We embed a lockdown choice in a simplified epidemiological model and derive formulas for the optimal lockdown intensity and duration. The optimal policy reflects the rate of time preference, epidemiological factors, the hazard rate of vaccine discovery, learning effects in the health care sector, and the severity of output losses due to a lockdown. In our baseline specification a Covid-19 shock as currently experienced by the US optimally triggers a reduction in economic activity by two thirds, for about 50 days, or approximately 9.5 percent of annual GDP.

More Endorsements for “Macroeconomic Analysis”

“This is an excellent textbook for macroeconomics at the master’s or beginning PhD level. The topics and the material used to cover them are well chosen; the treatment gives a solid and unified background for positive and normative analysis. It strikes a good balance between being conceptually clear and logically consistent, and at the same time quite accessible.”
Fernando Alvarez, Saieh Family Professor of Economics, University of Chicago

Forthcoming, MIT Press.
MIT Press book page. My book page.

More Endorsements for “Macroeconomic Analysis”

“Finally, a book that fills the longstanding, and growing, gap between existing undergraduate and graduate macroeconomics textbooks. The winning approach of the author is to rigorously develop the core insights in each topic studied, avoiding superfluous diversions. The emphasis on government policy and political economy is especially useful in interpreting current global macroeconomic events.”
Gianluca Violante, Professor of Economics, Princeton University
(To be continued.)

Forthcoming, MIT Press.
MIT Press book page. My book page.

More Endorsements for “Macroeconomic Analysis”

“Niepelt’s textbook provides a concise, but rigorous introduction to the key concepts, tools, and models that constitute modern macroeconomic theory. His pedagogical approach, introducing the key building blocks of the theory one at a time, and focusing on what is essential at each stage, should make the learning experience a pleasant one. I expect it to become a staple reference in first-year graduate courses.”
Jordi Galí, CREI, Universitat Pompeu Fabra and Barcelona GSE
(To be continued.)

Forthcoming, MIT Press.
MIT Press book page. My book page.

More Endorsements for “Macroeconomic Analysis”

“Macroeconomic Analysis is the rare textbook that is both comprehensive and rigorous, as well as concise and simple. By staying focused on the core model of dynamic macroeconomics, it elegantly navigates through many topics. After studying this book, students will be ready to join the exciting debates in modern macroeconomics.”
Ricardo Reis, A. W. Phillips Professor of Economics, London School of Economics and Political Science
(To be continued.)

Forthcoming, MIT Press. Book page.