Knowledge that Transforms

To study competition, innovation, and industry dynamics that arise as a result of their interaction, we develop a new oligopolistic general-equilibrium Schumpeterian growth model. This model ties together the endogenous growth, oligopolistic competition, and dynamic industrial organization literatures in a single unified framework. Within each industry, there are an endogenously determined number of large firms (“superstars”) that compete á la Cournot and a continuum of small firms which collectively constitute a competitive fringe. Firms dynamically choose their innovation strategies, cognizant of other firms' choices, and their entry and exit are endogenous. The model is consistent with the macroeconomic trends observed in the United States since the 1970s, such as the domination of industries by a small number of superstar firms, the rise of markups, market concentration, profits, and R&D spending, and the decline in business dynamism, productivity growth, and the labor share. It replicates the empirical relationship between innovation and competition within and across industries. As an application, we estimate the model to disentangle the effects of separate mechanisms on the structural transition observed in the United States, which yields striking results: (1) While the increase in the average markup causes a significant static welfare loss, this loss is overshadowed by the dynamic welfare gains from increased innovation in response to higher profit opportunities. (2) The increasing costs of innovation are found to be the primary determinant of lackluster productivity growth, i.e., ideas are getting harder to find.

Standard New Keynesian (NK) models feature an optimal inflation target well below 2%, limited welfare losses from business cycle fluctuations and long-term monetary neutrality. We develop an NK framework with endogenous productivity and downward nominal wage rigidity (DNWR) which challenges these results. The interaction between endogenous growth and DNWR generates asymmetric hysteresis effects on unemployment and R&D. As a consequence, the model features a nonvertical long-run Phillips curve and a trade-off between price distortions and output hysteresis that changes the welfare-maximizing inflation rate to above 2%. Deviations from the optimal target carry welfare costs multiple times those in traditional NK models. Taylor rules that respond to the unemployment rate address more effectively the asymmetric hysteresis in our model. Results are robust to the inclusion of the effective lower bound on interest rates.

The structure of the Social Security program presents a trade-off between benefit duration and size; individuals who claim early receive lower monthly payments. Surprisingly, even wealthy Americans with high life expectancies frequently claim benefits at the earliest eligibility age, a behavior inconsistent with conventional life-cycle theory predictions. In fact, there is a striking similarity in claiming ages across groups with vastly different life expectancies, wealth levels, and incentives to delay. This paper resolves this puzzle by introducing policy details and subjective beliefs about longevity and program rules into a rich, forward-looking life-cycle model. When included in the model, subjective beliefs substantially narrow the claiming-age gaps across education (college vs. non-college) and marital-status (married vs. single) groups. Specifically, differences in program beliefs alone account for 48.6% of the education claiming age gap and 75.1% of the marital status gap. Counterfactual policy simulations demonstrate that failing to account for these claiming mechanisms dramatically overstates individual responses to an increase in the normal retirement age and understates the resulting fiscal savings.

Over the past four decades, the U.S. economy has seen a decline in the share of young firms alongside a rise in the profit share of GDP. This paper explores how population aging contributes to these twin trends through a demand-side channel. The core hypothesis is that younger households exhibit lower consumer inertia—a tendency to stick with previously chosen products—than older households. As demand shifts toward more inertial consumers, entry becomes harder, incumbents raise markups, and market share tilts toward larger firms. To quantify this mechanism, I develop and calibrate a firm dynamics model with overlapping generations of consumers who differ in their degree of inertia. Using detailed micro data, I show that younger households are significantly less inertial. The model implies that population aging accounts for 20%–30% of the observed decline in young firms and rise in profits. Reduced-form evidence across U.S. states and product categories supports the model’s predictions.

We present a flexible and scalable computational framework integrating machine learning and optimization theory to solve dynamic adverse selection models with persistent private information and many types. Our approach reformulates the model into a numerically tractable structure that bypasses set-valued dynamic programming; we formally prove that, under verifiable conditions, this relaxation yields the solution to the original problem. The recast problem is solved via a parallelized value function iteration algorithm, where high-dimensional, nonlinear functions are approximated using Gaussian process regression combined with Bayesian active learning. We apply our framework to two previously intractable models: one with persistent hidden information involving up to ten types and another incorporating multiple persistent types and overreporting. Validation against known solutions and rigorous credibility measures confirms accuracy. Allowing overreporting significantly alters long-run contract outcomes, concentrating consumption away from extremes and smoothing utility promises over time.

In this paper, I document systematic heterogeneity in ownership and financing of firms across Eurozone countries. To rationalize these differences, I build a quantitative general equilibrium model of workers and entrepreneurs who choose debt and equity financing of their firms, subject to rich country-specific financial frictions. The novel data on firm ownership and financing, combined with the structure of the model, allows me to quantify the level of debt and equity frictions in each country. Quantitatively, I find much larger output effects from equity frictions: harmonizing them across countries would lead to nearly four times larger output effects compared to debt frictions, and removing them would increase aggregate output by 73% more. The larger impact on output is due not only to the estimated levels and dispersion of equity frictions but also to the greater risk sharing provided by equity, which further incentivizes entrepreneurs to expand their firms. Through their effect on risk sharing, equity frictions also rationalize the observed negative relationship between equity financing and wealth inequality. Quantitatively, they are responsible for over 70% of the explained variation in top wealth shares across countries.

This paper studies how municipal governments jointly manage spending, credit market borrowing, and a public employee pension system. I model governments as levered investors who must meet non-defaultable pension obligations and may value government spending more than citizens. I quantify the model using data on California cities, including a new record of fiscal emergencies, tax increases required to maintain essential city services. After the financial crisis depleted pension funds, cities engaged in excessive risk-taking: the fiscal emergency option encouraged gambling for resurrection that kept cities vulnerable to shocks well into the recovery. To correct this problem, a savings requirement works better than a restriction on risk-taking or a pension funding requirement. The policy experiments emphasize that effective policies need to target the combined pension and bond finances, as policies that only target one, such as a pension funding requirement, are undermined by endogenous changes to the other.

We experimentally study decentralized one-to-one matching markets with transfers. We vary the information available to participants, complete or incomplete, and the surplus structure, supermodular or submodular. Several insights emerge. First, while markets often culminate in efficient matchings, stability is more elusive, reflecting the difficulty of arranging attendant transfers. Second, incomplete information and submodularity present hurdles to efficiency and especially stability; their combination drastically diminishes stability's likelihood. Third, matchings form ``from the top down'' in complete-information supermodular markets, but exhibit many more and less-obviously ordered offers otherwise. Last, participants' market positions matter far more than their dynamic bargaining styles for outcomes.

We show that the emergence of new economic opportunities that draw women away from their traditional domestic roles has significantly influenced the adoption of religious veiling. We measure the prevalence of veiling among young women across Indonesia's districts for more than two decades by hand-coding around a quarter million photographs attached to Indonesia's public high school registers. To establish causality, we exploit exogenous variation generated by international demand for Indonesia's products, interacted with the gender and sectoral composition of local industries. Districts exposed to stronger positive economic shocks---and thus greater economic opportunities for women---exhibit higher rates of veiling adoption. Our findings suggest that veiling facilitates young women's participation in formal labor markets while safeguarding their personal and social image in society.

We estimate the impact of public pension incentives on labor supply far from the normal retirement age by exploiting Poland's switch from a Defined Benefit to a Notional Defined Contribution (NDC) scheme. This reform created a sharp cohort-based discontinuity in the link between current pension contributions and future benefits. Using this discontinuity and the universe of taxpayers, we estimate an employment elasticity with respect to the net return to work of 0.51 for men at ages 51-54. We estimate a lifecycle model to match these responses and discuss the broader implications of the reform. The shift to NDC reallocates work incentives over the lifecycle, strengthening incentives at younger ages, when labor supply is relatively inelastic, and weakening them at older ages, when labor supply is more elastic. This reallocation of work incentives tends to reduce aggregate lifecycle labor supply, which highlights the advantage of targeting pension incentives towards ages at which labor supply is most responsive.