Advanced Purchase Commitments for a Malaria Vaccine: Estimating Costs and Effectiveness

To overcome the problem of insufficient research and development (R&D) on vaccines for diseases concentrated in low-income countries, sponsors could commit to purchase viable vaccines if and when they are developed. One or more sponsors would commit to a minimum price that would be paid per person immunized for an eligible product, up to a certain number of individuals immunized. For additional purchases, the price would eventually drop to short-run marginal cost. If no suitable product were developed, no payments would be made. We estimate the offer size which would make the revenues from R&D investments on a malaria vaccine similar to revenues realized from investments in typical existing commercial pharmaceutical products, as well as the degree to which various contract models and assumptions would affect the cost-effectiveness of such a commitment for the case of a malaria vaccine. Under conservative assumptions, we document that the intervention would be highly cost-effective from a public health perspective. Sensitivity analyses suggest most characteristics of a hypothetical malaria vaccine would have little effect on the cost-effectiveness, but that the duration of protection against malaria conferred by a vaccine strongly affects potential cost-effectiveness. Readers can conduct their own sensitivity analyses employing a web-based spreadsheet tool.

Hidden Skewness: On the Difficulty of Multiplicative Compounding Under Random Shocks

Multiplicative growth processes that are subject to random shocks often have a skewed distribution of outcomes. In a number of incentivized laboratory experiments we show that a large majority of participants either strongly underestimate skewness or ignore it completely. Participants misperceive the outcome distribution’s spread to be far too narrow-band and they estimate the median to lie too close to the distribution’s center. The observed bias in expectations is irrespective to risk preferences and fairly robust to feedback. It is consistent with a behavioral model in which geometric growth is confused with linear growth. The misperception is a possible explanation of investors’ difficulties with real-world financial products like leveraged ETFs

Do we follow others when we should? A simple test of rational expectations

The paper presents a new meta data set covering 13 experiments on the social learning games by Bikhchandani, Hirshleifer, and Welch (1992). The large amount of data makes it possible to estimate the empirically optimal action for a large variety of decision situations and ask about the economic signi…cance of suboptimal play. For example, one can ask how much of the possible payo¤s the players earn in situations where it is empirically optimal that they follow others and contradict their own information. The answer is 53% on average across all experiments –only slightly more than what they would earn by choosing at random. The players’ own information carries much more weight in the choices than the information conveyed by other players’choices: the average player contradicts her own signal only if the empirical odds ratio of the own signal being wrong, conditional on all available information, is larger than 2:1, rather than 1:1 as would be implied by rational expectations. A regression analysis formulates a straightforward test of rational expectations, which rejects, and con…rms that the reluctance to follow others generates a large part of the observed variance in payo¤s, adding to the variance that is due to situational di¤erences

Beliefs and actions in the trust game : Creating instrumental variables to estimate the causal effect

In many economic contexts, an elusive variable of interest is the agent’s belief about relevant events, e.g. about other agents’ behavior. A growing number of surveys and experiments ask participants to state beliefs explicitly but little is known about the causal relation between beliefs and other behavioral variables. This paper discusses the possibility of creating exogenous instrumental variables for belief statements, by informing the agent about exogenous manipulations of the relevant events. We conduct trust game experiments where the amount sent back by the second player (trustee) is exogenously varied. The procedure allows detecting causal links from beliefs to actions under plausible assumptions. The IV-estimated effect is significant, confirming the causal role of beliefs. It is only slightly and insignificantly smaller than in estimations without instrumentation, consistent with a mild effect of social norms or other omitted variables.Publisher PD

Correlation neglect in financial decision-making

Good decision-making often requires people to perceive and handle a myriad of statistical correlations. Notably, optimal portfolio theory depends upon a sophisticated understanding of the correlation among financial assets. In this paper, we examine people's understanding of correlation using a sequence of portfolio-allocation problems and find it to be strongly imperfect. Our experiment uses pairs of portfolio-choice problems that have the same asset span|identical sets of attainable returns|and differ only in the assets' correlation. While any outcome-based theory of choice makes the same prediction across paired problems, subjects behave very differently across pairs. We find evidence for correlation neglect|treating correlated variables as uncorrelated|as well as for a form of \1/n heuristic"|investing half of wealth each of the two available assets

Risk, complexity, and deviations from expected-value maximization: results of a lottery choice experiment

Varying several parameters of single-stage lottery choice tasks we investigate the question which features of a decision task lead subjects to deviate from maximizing expected monetary value (EV). Despite small differences in EV between the two lotteries in the choice sets, the subjects on average chose the lottery with the higher EV in every task. Risk avoidance occurs, but not consistently over all tasks. Further results are that subjects prefer less complex lotteries over more complex ones, and that risk matters the more the less complex the decision task is