Knowledge that Transforms

This paper develops a new approach to change-point modelling that allows the number of change-points in the observed sample to be unknown. The model we develop assumes that regime durations have a Poisson distribution. It approximately nests the two most common approaches: the time-varying parameter (TVP) model with a change-point every period and the change-point model with a small number of regimes. We focus considerable attention on the construction of reasonable hierarchical priors both for regime durations and for the parameters that characterize each regime. A Markov chain Monte Carlo posterior sampler is constructed to estimate a version of our model, which allows for change in conditional means and variances. We show how real-time forecasting can be done in an efficient manner using sequential importance sampling. Our techniques are found to work well in an empirical exercise involving U.S. GDP growth and inflation. Empirical results suggest that the number of change-points is larger than previously estimated in these series and the implied model is similar to a TVP (with stochastic volatility) model.

This paper studies the effect of interest rates on investment in an environment where firms make irreversible investments with uncertain pay-offs. In this setting, changes in the interest rate affect both the cost of capital and the cost of delaying investment to acquire information. These two forces combine to generate an aggregate investment demand curve that is a backward-bending function of the interest rate. At low rates, increasing the interest rate raises investment by increasing the cost of delay.

Workers earn higher wages in cities vs. rural areas. This gap could arise because cities make workers more productive, or it could be the result of a non-random selection of workers into cities based on their ability and their endogenous history of career choices. To untangle these issues, this paper estimates a dynamic programming model, which embeds the choice of residing in a city or rural area within a model of career choices over time. After controlling for all the sources of selection and endogeneity, the estimates indicate that a given worker does earn more in the city for white-collar work, but not for blue-collar work. In addition, city work experience is found to be worth more than rural work experience in the rural area for white-collar work, but not for blue-collar work. These results support the interpretation that cities make white-collar workers more productive and suggest that workers may consider moving to the city not only in terms of locational choice, but also as a form of human capital investment.

This paper presents a model of international trade that features heterogeneous firms, relative endowment differences across countries, and consumer taste for variety. The paper demonstrates that firm reactions to trade liberalization generate endogenous Ricardian productivity responses at the industry level that magnify countries' comparative advantage. Focusing on the wide range of firmlevel reactions to falling trade costs, the model also shows that, as trade costs fall, firms in comparative advantage industries are more likely to export, that relative firm size and the relative number of firms increases more in comparative advantage industries and that job turnover is higher in comparative advantage industries than in comparative disadvantage industries.

An entrepreneur with limited liability needs to finance an infinite horizon investment project. An agency problem arises because she can divert operating cash flows before reporting them to the financiers. We first study the optimal contract in discrete time. This contract can be implemented by cash reserves, debt, and equity. The latter is split between the financiers and the entrepreneur and pays dividends when retained earnings reach a threshold. To provide appropriate incentives to the entrepreneur, the firm is downsized when it runs short of cash. We then study the continuous-time limit of the model. We prove the convergence of the discrete-time value functions and optimal contracts. Our analysis yields rich implications for the dynamics of security prices. Stock prices follow a diffusion reflected at the dividend barrier and absorbed at 0. Their volatility, as well as the leverage ratio of the firm, increase after bad performance. Stock prices and book-to-market ratios are in a non-monotonic relationship. A more severe agency problem entails lower price-earning ratios and firm liquidity and higher default risk.

Formal models of elections have emphasized the convergence of party leaders towards the centre of the electoral distribution. This paper attempts to resolve the apparent disparity between the formal result and the perception of political divergence by considering a model incorporating valence. Valence can be interpreted as the non-policy basis of political judgement made by the electorate concerning the quality of political contenders. The theorem presented here shows that there is a necessary condition for convergence. The condition involves the difference in party valences and the electoral variance. When the condition fails, the low-valence parties will be forced to adopt policy positions far from the electoral centre. The inference appears to be substantiated by an empirical model of the Israel election in 1996.

Autocrats in many developing countries have extracted enormous personal rents from power. In addition, they have imposed inefficient policies including pervasive patronage spending. I present a model in which the presence of ethnic identities and the absence of institutionalized succession processes allow the ruler to elicit support from a sizeable share of the population despite large reductions in welfare. The fear of falling under an equally inefficient and venal ruler that favours another group is enough to discipline supporters. The model predicts extensive use of patronage, ethnic bias in taxation, and spending patterns and unveils a new mechanism through which economic frictions translate into increased rent extraction by the leader. These predictions are consistent with the experiences of bad governance, ethnic bias, wasteful policies, and kleptocracy in post-colonial Africa.

We analyze a situation where a monopolist is selling an indivisible good to risk neutral buyers who only have an estimate of their private valuations. The seller can release, without observing, certain additional signals that affect the buyers’ valuations. Our main result is that in the expected revenue maximizing mechanism, the seller makes available all the information that she can, and her expected revenue is the same as it would be if she could observe the part of the information that is “new” to the buyers. We also show that this mechanism can be implemented by what we call a handicap auction in interesting applications. In the first round of this auction, each buyer picks a price premium from a menu offered by the seller (a smaller premium costs more). Then the seller releases the additional signals. In the second round, the buyers bid in a second-price auction where the winner pays the sum of his premium and the second highest non-negative bid. In the case of a single buyer, this mechanism simplifies to a menu of European call options.

Experts often collect and report information over time. What reporting protocol elicits the most information? Here, a principal receives reports sequentially from an agent with privately known ability, who observes two signals about the state of the world. The signals differ in initial quality and, unlike previous work, differ in quality improvement. The paper finds that “mind changes” (inconsistent reports) can signal talent if a smart agent improves faster. Also, sequential reports dominate when the principal's decision is very sensitive to information; a single report dominates if the mediocre agent's signals improve faster or the agent is likely mediocre.

We endogenize preferences using the “indirect evolutionary approach”. Individuals are randomly matched to play a two-person game. Individual (subjective) preferences determine their behaviour and may differ from the actual (objective) pay-offs that determine fitness. Matched individuals may observe the opponents' preferences perfectly, not at all, or with some in-between probability. When preferences are observable, a stable outcome must be efficient. When they are not observable, a stable outcome must be a Nash equilibrium and all strict equilibria are stable. We show that, for pure-strategy outcomes, these conclusions are robust to allowing almost perfect, and almost no, observability, with the notable exception that inefficient strict equilibria may fail to be stable with any arbitrarily small degree of observability (despite being stable with no observability).