We study production functions with capital and labor as arguments that exhibit positive, yet diminishing marginal products and constant returns to scale. We show that such functions satisfy the Inada conditions if (i) both inputs are essential and (ii) an unbounded quantity of either input leads to unbounded output. This allows for an alternative characterization of the neoclassical production function that altogether dispenses with the Inada conditions. Although this proposition generalizes to the case of n > 2 factors of production, its converse does not hold: 2n Inada conditions do not imply that each factor is essential.

We develop a model with financial frictions and sovereign default risk wherein the maturity of public debt is allowed to be larger than one period. When the debt portfolio has longer average maturities, public debt increases less in the event of a crisis, reducing the size of the subsequent fiscal consolidation through distorsionary taxes or public spending, with positive effects on welfare. In addition, we provide some results suggesting that optimized fiscal responses to a crisis depend on the average maturity of the debt portfolio.

This paper examines optimal policy in a macroeconomic model with collateral constraints. Binding collateral constraints yield inefficient competitive equilibrium allocations because they distort the optimal utilization of real resources. I identify the set of policy instruments that can be used by a Ramsey planner to achieve the first-best and the second-best (i.e., constrained planner's) allocations. A system of distortionary taxes on capital and labor income, along with direct lump-sum transfers among borrowers and lenders replicates the first-best outcome. The tax rates correct for the marginal distortions, whereas the direct lump-sum transfers perform income redistributions among the agents. In absence of direct lump-sum transfers, the distortionary taxes have an additional role, i.e., to perform implicit income transfers, and only second-best outcomes are attainable. I also derive the optimal policy in response to real and financial shocks, and show how the policy recommendations differ depending on the set of policy instruments available.

How much should society invest in medical care that extends the lives of the older generations? We derive a golden rule for the level of health care expenditures and find that the optimal level of life-extending health care expenditures should increase with rising productivity, increase with the retirement age, and also increase with the population growth rate if a higher growth rate lowers the ratio of retirees to working-age people sufficiently, while the effects of an improvement in medical technology are ambiguous. Moreover, we find that a market economy may be inefficient in terms of the provision of life-extending health care because an individual ignores the effect of his own longevity on the income of others.

I analyze the impact of intellectual property and product market competition regulations on innovation and long-run growth in an endogenous growth model with two R&D performing sectors. I show that strengthening intellectual property rights and competition in a sector increases its R&D investments. However, these policies adversely affect R&D investments in the other sector because of increased factor competition between the sectors. As a result, the overall impact of such policies on economic growth is ambiguous. I perform a numerical exercise in an attempt to resolve this ambiguity. This exercise suggests that strengthening intellectual property rights increases economic growth, but higher competition has a very limited effect on growth.

This study investigates the labor market under increased automation of middle-skilled jobs wherein worker suitability for these jobs is considered. We examine two effects of increased automation on workers. The first effect is the possibility of replacement of middle-skilled workers by machines. The second effect is the diversity in job mismatch probabilities of workers. If machines perform a worker’s suitable jobs more (or less) than the worker’s unsuitable jobs, then the worker’s job mismatch probability rises (or declines). Because workers who have larger job mismatch probabilities remain job seekers, it is more difficult for a firm to find a suitable worker. Due to these two effects, underemployment rises.

One usually identifies bubble solutions to linear rational expectations models by extra components (irrelevant lags) arising in addition to market fundamentals. Although there are still many solutions relying on a minimal set of state variables, i.e., relating in equilibrium the current state of the economic system to as many lags as initial conditions, there is a conventional wisdom that the bubble-free (fundamentals) solution should be unique. This paper examines the existence of endogenous stochastic sunspot fluctuations close to solutions relying on a minimal set of state variables, which provides a natural test for identifying bubble and bubble-free solutions. It turns out that only one solution is locally immune to sunspots, independently of the stability properties of the perfect-foresight dynamics. In the standard saddle-point configuration for these dynamics, this solution corresponds to the so-called saddle stable path.

This paper shows how fiscal policy affects unemployment in a New Keynesian model with search and matching frictions and distortionary taxation. The model is estimated using US data that includes labor market flows and distinct fiscal instruments. Several findings stand out. First, unemployment multipliers for spending and consumption tax cuts are substantial, even though output multipliers turn out to be less than one. Second, multipliers for labor tax cuts are small. Third, fiscal rules enhance the positive effects of discretionary fiscal policy. However, these expansionary effects on the multipliers are modest compared to earlier studies.

This paper studies how search externalities and wage bargaining distort vacancy creation and the allocation of workers to jobs in markets with two-sided heterogeneity. To do so, I propose a model of a frictional labor market where heterogeneous workers decide which job to look for and firms decide which technology to adopt. At equilibrium, there is perfect segmentation across sectors, which is determined by a unique threshold of workers' productivity. This threshold is inefficient because of participation and composition externalities. The Pigouvian tax scheme that decentralizes optimal sorting shows that these externalities have opposite signs. Furthermore, their relative strength depends on the distribution of workers' skills, so that when there are many (few) skilled workers, too many (few) high-technology jobs are created.

By studying complete and incomplete dynamic financial markets, I show that if some agents are money-illusioned and neglect inflation, the rational agents who are aware of inflation are driven out of the market in the long run, in the sense that the money-illusioned agents consume the economy's entire endowment. The reason for this finding is that with inflation, the money-illusioned agents always believe that the return on their savings is higher than it actually is. Because these agents trade financial assets in markets with the rational agents, the rational agents end up being borrowers and the money-illusioned agents lenders. Because the rational agents' debt accumulates over time, they become so indebted that the money-illusioned agents eventually consume the economy's entire endowment. If there is deflation, the opposite is true, and the rational agents evolutionarily dominate.

In this paper, we study the positive and normative implications of financial shocks in a standard New Keynesian model that includes banks and frictions in the market for bank capital. We show how such frictions influence materially the effects of bank liquidity shocks and the properties of optimal policy. In particular, they limit the scope for countercyclical monetary policy in the face of these shocks. A fiscal policy instrument can complement monetary policy by offsetting the balance-sheet effects of these shocks, and jointly optimal policies attain the same equilibrium that monetary policy (alone) could attain in the absence of equity-market frictions.

This study introduces automation into a Schumpeterian growth model to explore the effects of R&D and automation subsidies. R&D subsidy increases innovation and growth but decreases the share of automated industries and the degree of capital intensity in the aggregate production function. Automation subsidy has the opposite effects on these macroeconomic variables. Calibrating the model to US data, we find that raising R&D subsidy increases the welfare of high-skill workers but decreases the welfare of low-skill workers and capital owners, whereas increasing automation subsidy increases the welfare of high-skill workers and capital owners but decreases the welfare of low-skill workers. Therefore, whether the government should subsidize innovation or automation depends on how it evaluates the welfare gains and losses of different agents in the economy.

This paper analyzes whether the Fed had the ability through its conventional monetary policy to affect key economic and financial variables, and, in particular, the term structure of interest rates, during the recent financial crisis. This departs from the empirical literature that focuses mainly on the effectiveness of unconventional monetary policies during this episode, although these policies are appropriate only to the extent that the conventional policy was ineffective in the first place. Our identification strategy based on the conditional heteroskedasticity of the structural innovations allows us to specify a flexible structural vector auto-regressive process that relaxes the identifying assumptions commonly used in earlier studies. Comparing our results obtained from samples excluding and including the financial crisis, we find that the conventional monetary policy has lost its effectiveness shortly after the beginning of the financial turmoil. This result suggests that the Fed's use of unconventional policies was appropriate, at least, with the objective of changing the term structure of interest rates.

The objective of this book is to provide “a systematic theory of endogenous business fluctuations and growth with a hierarchical structure of integrated macro-dynamical models” (p. 372). The starting point is Tobin's neoclassical model of monetary growth, and successive chapters show how Tobin's model can be extended in various “realistic” directions while preserving the relevant adding-up and balance-sheet constraints of a macro model. The work reported here is squarely in an ongoing European theoretical tradition that eschews the stochastic, representative-agent, approach to macroeconomic modeling. Absent stochastic disturbances, the authors provide a qualitative analysis of dynamic behavior for a variety of closed-economy models—a variety that, as the authors themselves point out, is closely related to three prototype models studied in Part I of Sargent's 1977 book, Macroeconomic Theory.

This paper develops a theory of human capital to investigate the role of early childhood health in explaining the large and persistent schooling gaps observed within and across countries. Quantitative analysis using the theory and data from 98 countries shows that early health inequalities within developingcountries strongly amplify later schooling gaps— counterfactually eliminating inequalities reduces schooling Ginis by an average of 18% in developing economies but has only mild effects in richer countries. Moreover, early health inequalities are found to be an important source of schooling variation across countries— universally equating early health to the average US level reduces the cross-country standard deviation of average schooling attainment by over 40%. Additional policy experiments reveal that the gains from early health interventions tend to be amplified by later educational investments in developing economies, while those targeting school-aged children may be limited if early health conditions are ignored.

This paper applies the common stochastic trends representation approach to the time series of total factor productivity (TFP) and the relative price of investment (RPI) to investigate the modeling of neutral technology (NT) and investment-specific technology (IST) and its econometric ramifications on the analysis of general equilibrium model. The permanent and transitory movements in both series are estimated efficiently via Markov chain Monte Carlo methods using band matrix algorithms. The results indicate that TFP and the RPI are, each, well represented by a differenced first-order autoregressive process. In addition, their time series share a common trend component that we interpret as reflecting changes in general purpose technology. These results are consistent with studies that suggest that (1) the traditional view of assuming that NT and IST follow independent processes is not supported by the features of the time series and (2) improper specification of secular trends may distort estimation and inference. Notably, the findings provide some guidance to minimize the effect of idiosyncratic and common trend misspecifications on the analysis of impulse dynamics and propagation mechanisms in macroeconomic models.

An estimated Markov-switching DSGE modeling framework that allows for parameter shifts across regimes is employed to test the hypothesis of regime-dependent credibility of Hong Kong's linked exchange rate system. The baseline model distinguishes two regimes with respect to the time-series properties of the risk premium. Regime-dependent impulse responses to macroeconomic shocks reveal substantial differences in spreads. To test the sensitivity of the results, a number of robustness checks are performed. The findings contribute to efforts at modeling exchange rate regime credibility as a nonlinear process with two distinct regimes.

The global financial crisis was characterized by heightened financial risk in the USA, which spread to the rest of the world, including emerging economies. This paper constructs a core–periphery model with a global banking network and financial frictions. Due to a common-lender effect, when global banks lend to an emerging economy, heightened financial risk in the center depresses cross-border lending to the emerging economy, reducing real activities and exacerbating monetary policy trade-offs. As financial markets become more integrated, exchange rate flexibility becomes less welfare enhancing and active capital account policy becomes more welfare enhancing.

Over the past few decades, both the relative price of housing structures and housing services consumption relative to nondurables increased significantly in the United States. This paper explores demand-side factors such as an increase in idiosyncratic earnings risks and changes in housing institutions as potential explanations for the phenomenon. We build a general equilibrium incomplete markets model of housing and compare two steady states that correspond to the 1967 and 2000 U.S. economies. Our model can generate the simultaneous increase in the relative price of houses and housing services consumption relative to nondurables. We find that the increased earnings risks are crucial in replicating this pattern.

Introducing susceptible-infected-recovered epidemiology dynamics with vaccines into an endogenous growth model, we investigate the impact of government infectious disease policy on macroeconomic performance. We find that any expenditure that improves health, whether to reduce the contact rate or increase the recovery rate or the vaccination rate, and regardless of whether it comes directly from the households or the government, has a positive impact on economic growth, but does not necessarily improve the welfare. The reason people’s health has improved but their welfare has fallen is because government expenditures must be covered by taxes, which will reduce their disposable income and consumption.