Knowledge that Transforms

We study optimal taxation of bequests and inter vivos transfers in a model where altruistic parents and their offspring disagree on intertemporal trade-offs. We show that the laissez-faire equilibrium is Pareto inefficient, and whenever offspring are impatient from their parents' perspective, optimal policy involves a positive tax on parental transfers. Cautioned by the technical complications present in this class of models, our normative prescriptions do not rely on the assumption of differentiability of the agents' policy functions.

This article presents a dynamic general equilibrium model to investigate how different contracting modes based on formal and relational enforcements emerge endogenously and are linked dynamically with the process of economic development. Formal contracts are enforced by third-party institutions (courts), whereas relational contracts are self-enforcing agreements without third-party involvement. The novel feature of our model is that it demonstrates the co-evolution of these different enforcement modes and market equilibrium conditions, all of which are jointly determined. We then characterize the equilibrium paths of such dynamic processes and show the time structure of relational contracting in the process of development. In particular, we show that relational contracting fosters the emergence of a market-based economy in the growth phase of development; however, its role declines as the economy enters a mature phase.

We define a class of dynamic Markovian games, directional dynamic games (DDG), where directionality is represented by a strategy-independent partial order on the state space. We show that many games are DDGs, yet none of the existing algorithms are guaranteed to find any Markov perfect equilibrium (MPE) of these games, much less all of them. We propose a fast and robust generalization of backward induction we call state recursion that operates on a decomposition of the overall DDG into a finite number of more tractable stage games , which can be solved recursively. We provide conditions under which state recursion finds at least one MPE of the overall DDG and introduce a recursive lexicographic search (RLS) algorithm that systematically and efficiently uses state recursion to find all MPE of the overall game in a finite number of steps. We apply RLS to find all MPE of a dynamic model of Bertrand price competition with cost-reducing investments which we show is a DDG. We provide an exact non-iterative algorithm that finds all MPE of every stage game, and prove there can be only 1, 3, or 5 of them. Using the stage games as building blocks, RLS rapidly finds and enumerates all MPE of the overall game. RLS finds a unique MPE for an alternating move version of the leapfrogging game when technology improves with probability 1, but in other cases, and in any simultaneous move version of the game, it finds a huge multiplicity of MPE that explode exponentially as the number of possible cost states increases.

We link daily air pollution exposure to measures of contemporaneous health for communities surrounding the twelve largest airports in California. These airports are some of the largest sources of air pollution in the US, and they experience large changes in daily air pollution emissions depending on the amount of time planes spend idling on the tarmac. Excess airplane idling, measured as residual daily taxi time, is due to network delays originating in the Eastern US. This idiosyncratic variation in daily airplane taxi time significantly impacts the health of local residents, largely driven by increased levels of carbon monoxide (CO) exposure. We use this variation in daily airport congestion to estimate the population dose-response of health outcomes to daily CO exposure, examining hospitalization rates for asthma, respiratory, and heart-related emergency room admissions. A one standard deviation increase in daily pollution levels leads to an additional $540 thousand in hospitalization costs for respiratory and heart-related admissions for the 6 million individuals living within 10 km (6.2 miles) of the airports in California. These health effects occur at levels of CO exposure far below existing Environmental Protection Agency mandates, and our results suggest there may be sizable morbidity benefits from lowering the existing CO standard.

This article develops an empirical framework for analysing the timing of international treaties. A treaty is modelled as a dynamic game among governments that decide on participation in every period. The net benefit of treaty membership increases over time. Spillovers among members and non-members accelerate or delay treaty formation by transforming participation into a strategic complement or substitute, respectively. The predictions of the model inform the estimation of the structural parameters, based on a cross section of treaty ratification dates. With this approach, I estimate the sign and magnitude of strategic interaction in the ratification of the Montreal Protocol, in the formation of Europe's preferential trade agreements, and in the growth of Germany's network of bilateral investment treaties. Through a series of counterfactual experiments, I explore different mechanisms that give rise to strategic interaction in the formation of these treaties.

The increase in the information that firms can collect or purchase about network effects across consumers motivates two important questions: how does a firm's pricing strategy react to detailed information on network effects? Are the availability and use of such information beneficial or detrimental to consumer surplus? We develop a model in which a monopoly sells a network good and price discriminates based on information about consumers' influence and consumers' susceptibility to influence. The monopoly optimally offers consumers price discounts for their influence and charges price premia for their susceptibility; the price premia and the price discounts are simple functions of the pattern of network effects. We determine under which conditions, relative to uniform price, consumer surplus increases, and we characterize the value of information on network effects for the monopoly.

This paper studies a model of long-term contracting for experimentation. We consider a principal–agent relationship with adverse selection on the agent’s ability, dynamic moral hazard, and private learning about project quality. We find that each of these elements plays an essential role in structuring dynamic incentives, and it is only their interaction that generally precludes efficiency. Our model permits an explicit characterization of optimal contracts.

We use probabilistic expectations data elicited from survey respondents in rural Malawi to investigate how risky sexual behaviour may be influenced by individuals' expectations about survival, and future HIV status, which in turn depend on the perceived impact of HIV/AIDS on survival, expectations about own and partner's current HIV status, and expectations about HIV transmission rates. Subjective expectations, in particular about mortality risk but not the risk of living with HIV, play an important role in determining the decision to have multiple sexual partners. Using our estimated parameters, we simulate the impact of various policies that would influence expectations. An information campaign on mortality risk would decrease risky sexual behaviour on average, whereas an information campaign on HIV transmission risks, which tend to be overestimated by respondents, would actually increase risky behaviour. Also, the expansion of anti-retroviral therapy (ART) treatments to all individuals infected with HIV would increase risky sexual behaviour for a quarter of the HIV-negative individuals or those who have not been tested because they are aware that ART increases life expectancy, and thus reduces the cost of becoming HIV positive.

This paper investigates the role of inter-city transport costs in determining the income of sub-Saharan African cities. In particular, focusing on fifteen countries whose largest city is a port, I find that an oil price increase of the magnitude experienced between 2002 and 2008 induces the income of cities near that port to increase by 7 percent relative to otherwise identical cities 500 kilometers farther away. Combined with external estimates, this implies an elasticity of city economic activity with respect to transport costs of -0.28 at 500 kilometers from the port. Moreover, the effect differs by the surface of roads between cities. Cities connected to the port by paved roads are chiefly affected by transport costs to the port, while cities connected to the port by unpaved roads are more affected by connections to secondary centers.

We study sales techniques which discourage consumer search by making it harder or more expensive to return to buy after a search for alternatives. It is unilaterally profitable for a seller to deter search under mild conditions, but sellers can suffer when all do so. When a seller cannot commit to its policy, it exploits the inference that those consumers who try to buy later have no good alternative, and in many cases the outcome is as if the seller must make an exploding offer. Search deterrence results in sub-optimal matching of products to consumers and often raises the price consumers pay.