Christian Rojas

Eliciting Risk Preferences: When is Simple Better?

We study the estimation of risk aversion preferences with experimental data. The focus is on the trade-offs that arise when choosing between two different elicitation methods that have different degrees of difficulty for subjects. We analyze how and when the simpler, but coarser, elicitation method may be preferred to the more complex, but finer, one. Results indicate that the more complex measure has an overall superior predictive accuracy, but its downside is that subjects exhibit noisier behavior; conversely, the simpler measure has the opposite costs and benefits. Our main result is that subjects’ numerical skills can help better assess this tradeoff: the simpler task may be preferred when subjects exhibit low numeracy as it generates less noisy behavior but similar predictive accuracy than the more complex task; conversely, for subjects with higher numerical skills, the greater predictive accuracy of the more complex task more than outweighs the larger noise. We explore timeconsistency and preference heterogeneity under the two methods and provide methodological suggestions for future work.

Debt Aversion and the Demand for Loans for Postsecondary Education

The authors report the results of an experiment designed to measure the impact of different forms of subsidies on the demand for postsecondary education financing among a sample of adults ages 18–55 in Canada. The experiment presents subjects with a series of choices involving trade-offs between cash payments and grants or loans earmarked for full or part-time education. In addition, the experiment includes experimental measures of time and risk preferences, and an extensive survey of experience and attitudes. This article focuses on the role of a persons attitudes toward debt (debt aversion) and experience with debt (debt use) in the decision to take up subsidized loans for postsecondary education. Using survey measures, the authors find no evidence that debt aversion is an important barrier to investment in postsecondary education. In addition, subjects with experience carrying and managing debt are more willing than others to take on additional debt to finance postsecondary education.

PRICE COMPETITION IN U.S. BREWING

This study utilizes a brand-level dataset that captures a unique natural experiment, a 100% increase in the excise tax, to evaluate different pricing models in the U.S. beer industry. To assess the plausibility of different models, the increase in marginal cost resulting from the tax increase is exploited: observed prices in the post-increase period are compared to the prices that should be observed under various pricing models. Three types of models are analyzed: Bertrand-Nash, leadership, and collusion. Results indicate that extreme cases of collusion can be confidently ruled out while several models may explain the observed prices equally well.

WHAT HAPPENS WHEN DEMAND IS ESTIMATED WITH A MISSPECIFIED MODEL

We conduct Monte Carlo experiments to investigate the biases of assuming a misspecified demand model. We study continuous models (linear, log-linear and AIDS), and discrete choice models (logit) in the context of differentiated products and aggregate data. Estimating demand with the wrong model yields varying degrees of bias in estimated elasticities, but the logit model can yield unbiased estimates for a certain size of the assumed market potential. Merger simulations confirm the key importance of market potential in logit estimation suggesting that a discrete choice model may be preferable even when the discreteness of the purchase decision is questionable.

Market Power and the Lerner Index: A Classroom Experiment

We describe a classroom experiment that illustrates the concepts of market power and the Lerner Index. Students are organized in groups, each making a decision for a monopolist. Monopolists face different (unknown) demand curves, each with a different (constant) elasticity. Through repetition, students discover the profit maximizing solution and find that different monopolies have different mark-ups. The experimenter then reveals the unknown demand curves and illustrates how different elasticities are graphically and numerically connected to mark-ups and the Lerner index. The experiment can be used in a wide variety of courses including principles of economics, intermediate microeconomics, industrial organization, international trade, managerial economics and MBA classes. The experimental design is flexible: it can accommodate different class sizes (ranging from 10 to 100+ students) as well as different demand parameterizations. Finally, to reinforce the economic concept of profit maximization (MR=MC) in this setting, we also suggest and describe the implementation of an exercise based on the experimental design.

(Im)Patience Among Adolescents: A Methodological Note

Time preference is a fundamental component of many economic models and questions of interest. Yet, elicited preferences are frequently questioned on the grounds of potentially confounding elements of the experimental design, such as trust in the experimenter. We report on a time preference experiment using a sample of 490 high school students from Houston, TX and St. Cloud, MN. We find no relationship between confidence in receiving payment from the experimenters and the intertemporal allocation decisions. However, we find an illogical result for this population: reverse hyperbolic discounting. On aggregate the students are more likely to be impatient as choices are moved further into the future. However, this aggregate result is driven by heterogeneity in the home environment: For a subset of our population, elicited time preferences reflect increasing impatience as the decisions are farther in the future: These individuals come from home environments with factors that decrease the likelihood that they will receive the later payments. Once this heterogeneity is accounted for, the population is, on average, exponentially discounting. Results indicate that caution is warranted when trying to generalize results based on the convenience sample of university undergraduates to other populations. Further, results highlight the importance of accounting for preference heterogeneity within and across samples.

Price discrimination and resale: A classroom experiment

The authors present a classroom experiment designed to illustrate key concepts of third-degree price discrimination. By participating as buyers and sellers, students actively learn (1) how group pricing differs from uniform pricing, (2) how resale between buyers limits a sellers ability to price discriminate, and (3) how preventing price discrimination might reduce welfare. The exercise challenges sellers to set optimal prices against unknown demand curves by using a concrete story of pharmaceutical pricing to American and Mexican consumers. By working through profit calculations, students arrive at the optimal seller prices in three different settings: uniform pricing, price discrimination to two groups, and price discrimination to two groups who can resell to each other. The experimental design encourages students to converge reliably to the theoretical predictions. Classroom discussion can focus on real-world examples of price discrimination and on regulatory policy questions in industrial organization and international trade.

How much is an incoming message worth? Estimating the call externality

A feature of electronic communication markets is that a consumers decision to join or use a communications network can generate two effects on other users of the network: a network externality and a call externality. The former effect is defined as the benefit that users receive when a new subscriber joins the network (an expanded customer base can now be reached). The existence and magnitude of this effect is important from both theoretical and policy points of view. As a consequence, its empirical importance in various network markets has been documented in the literature. A call externality is defined as the benefit that a consumer derives when receiving a message (e.g. call) from another user, and it plays a crucial role both in the equilibrium predictions of theories of network competition and in the results of recent empirical work; however, as opposed to the network externality, no attempt has been made to quantify its empirical importance. In this paper I report results of a study designed to elicit and estimate the call externality. The data were generated using a stated-preference choice experiment designed to match theory and several characteristics of the mobile industry in Ecuador. To enhance the external validity of the results, the choice experiment was administered to over 2,500 individuals using 492 different internet-equipped government-run locations throughout the country. I find that call externalities are quite important in this market, but that their intensity depends heavily on the type of call (on-net v. off-net) as well as on the type of user (pre-paid v. post-paid). The call externality parameter for on-net calls is estimated at 0.67, while the significance of the call externality for off-net calls is significantly smaller (economically and statistically). Further, I find that the existence of call externalities in the market are mostly driven by pre-paid users.

Eliminating the Outside Good Bias in Logit Models of Demand with Aggregate Data

The logit model is the most popular tool in estimating demand for differentiated products. In this model, the outside good plays a crucial role because it allows consumers to stop buying the differentiated good altogether if all brands simultaneously become less attractive (e.g. if a simultaneous price increase occurs). But practitioners lack data on the outside good when only aggregate data are available. The currently accepted procedure is to assume a “market potential” that implicitly defines the size of the outside good (i.e. the number of consumers who considered the product but did not purchase); in practice, this means that an endogenous quantity is approximated by a reasonable guess thereby introducing the possibility of an additional source of error and, most importantly, bias. We provide two contributions in this paper. First, we show that structural parameters can be substantially biased when the assumed market potential does not approximate the outside option correctly. Second, we show how to use panel data techniques to produce unbiased structural estimates by treating the market potential as an unobservable in both the simple and the random coefficients logit demand model. We explore three possible solutions: (a) controlling for the unobservable with market fixed effects, (b) specifying the unobservable to be a linear function of product characteristics, and (c) using a “demeaned regression” approach. Solution (a) is feasible (and preferable) when the number of goods is large relative to the number of markets, whereas (b) and (c) are attractive when the number of markets is too large (as in most applications in Marketing). Importantly, we find that all three solutions are nearly as effective in removing the bias. We demonstrate our two contributions in the simple and random coefficients versions of the logit model via Monte Carlo experiments and with data from the automobile and breakfast cereals markets.

The Effect of Mandated Exclusive Territories in the US Brewing Industry

Theories on the welfare and competitive effects of exclusive territories are numerous, yet they provide ambiguous results. This paper exploits a natural experiment in the U.S. brewing industry to identify the direction of change in welfare caused by the use of exclusive territories. On January 31, 1991, the state of Arkansas enacted legislation which mandated all beer manufacturers to have exclusive territory clauses in their agreements with distributors. To identify the effect, I employ brand-level sales data before and after the legal change both in Arkansas as well as in nearby Oklahoma and Texas. Results are broadly consistent with a positive relationship between the use of exclusive territories and welfare: the most credible results suggest that the legal mandate increased brand-level volume sales by 45%. I conduct several falsification exercises and robustness tests to rule out other possible explanations for this large effect.