Working papers are not yet published, but are essentially complete papers.
Location Discrimination in Circular City, Torus Town, and Beyond, Oct. '99
I generalize Salop's "Circular City" model of spatial competition to spaces of arbitrary integer dimension, and to "transportation" costs which are an arbitrary positive power of distance. Assuming free entry, mill (i.e., non-discriminatory) pricing is compared to price discrimination based on customer locations. For all dimensions above one, there is some non-negative cost-power below which there is too little entry and above which there is too much. This cutoff cost-power rises with increasing dimension, and is larger under price discrimination. Mill pricing induces more entry for powers of four or less, and less entry for powers of five or more. Overall, too much entry seems a more severe problem than too little entry. For moderate powers and dimensions, this tends to favor price discrimination.
Warning Labels as Cheap Talk: Why Regulators Ban Products, Nov. '96
The most frequently mentioned explanation for product bans is that regulators know more about product quality than consumers. A problem with this explanation, however, is that such regulators should prefer to just communicate the information implicit in their ban, perhaps via a ``would have banned" label. We show, however, that since product labeling is cheap talk, any small market failure, such as a use-externality, will tempt regulators to lie about quality. If consumers suspect such lies, regulators can not communicate their ban information, and so will ban instead. We also show that when regulators expect market failures to lead to underconsumption of a product, and so would not ban it for informed consumers, regulators should want to commit to not banning this product for uninformed consumers.
For Savvy Bayesian Wannabes, Disagreements Are Not About Information, May '97
Consider two agents who want to be Bayesians with a common prior, but who can not due to severe computational limitations. If these agents are aware of certain easy-to-compute implications of these limitations, then they can agree to disagree about their estimate of a random variable only if they agree to disagree (to a similar degree) about both their average errors. Yet average error can in principle be computed independently of any agent's private information. Thus disagreements must be fundamentally about priors or computation, rather than about the actual state of the world.
Patterns of Patronage -- Why Grants Won Over Prizes in Science. first version May 1995.
Prizes were a common way to patronize basic research in the eighteenth century. Science historians say grants then won over prizes because grants are a superior institution. If different patron types tend to use different patronage forms, however, perhaps the patron types who tend to use grants just became more common.
To test this hypothesis, I estimate the use of prize-like vs. grant-like funding among eighteenth century scientific societies. Societies with non-autocratic, non-local government patrons were especially likely to use grant-like funding. As these are today's dominant patrons of basic research, eighteenth century data successfully predicts current patronage forms.
Burning the Cosmic Commons: Evolutionary Strategies for Interstellar Colonization, Mar. '98
Attempts to model interstellar colonization may seem hopelessly compromised by uncertainties regarding the technologies and preferences of advanced civilizations. If light speed limits travel speeds, however, then a selection effect may eventually determine frontier behavior. Making weak assumptions about colonization technology, we use this selection effect to predict colonists' behavior, including which oases they colonize, how long they stay there, how many seeds they then launch, how fast and far those seeds fly, and how behavior changes with increasing congestion. This colonization model explains several astrophysical puzzles, predicting lone oases like ours, amid large quiet regions with vast unused resources.
Must Early Life Be Easy? The Rythm of Major Evolutionary Transitions. first version Sept. 1996.
If we are not to conclude that most planets like Earth have evolved life as intelligent as we are, we must presume Earth is not random. This selection effect, however, also implies that the origin of life need not be as easy as the early appearance of life on Earth suggests. If a series of major evolutionary transitions were required to produce intelligent life, selection implies that a subset of these were ``critical steps," with durations that are similarly distributed. The time remaining from now until simple life is no longer possible on Earth must also be similarly distributed. I show how these results provide timing tests to constrain models of critical evolutionary transitions.
Economic Growth Given Machine Intelligence, Aug.? '98
A simple exogenous growth model gives conservative estimates of the economic implications of machine intelligence. Machines complement human labor when they become more productive at the jobs they perform, but machines also substitute for human labor by taking over human jobs. At first, expensive hardware and software does only the few jobs where computers have the strongest advantage over humans. Eventually, computers do most jobs. At first, complementary effects dominate, and human wages rise with computer productivity. But eventually substitution can dominate, making wages fall as fast as computer prices now do. An intelligence population explosion makes per-intelligence consumption fall this fast, while economic growth rates rise by an order of magnitude or more. These results are robust to automating incrementally, and to distinguishing hardware, software, and human capital from other forms of capital.
Showing That You Care: The Evolution of Health Altruism. May '99.
Altruism, or directly caring about the outcomes of others, is often suggested as an important explanation for otherwise puzzling phenomena in health policy. There are many possible ``altruists," however, depending on which people and outcomes the altruist cares about. I propose a specific model of health altruism that 1) fits with what we know about our ancestors' behavior and environment, and 2) accounts for several health policy puzzles. It assumes that altruism was directed toward social allies, that allies prevented health-harming crisis events, and that some people knew things that others did not about who would remain an ally. This model then offers a simple unified explanation of: a) regulatory paternalism, especially toward the low status, b) value-driven support for national health insurance, c) the social-status health-gradient, and d) the near-zero marginal health-value of medical care.
Long-Term Growth As A Sequence of Exponential Modes. Sept. '98.
The long-term history of world economic growth seems to be describable as sequence of exponential growth modes. In the current mode, which has lasted about 70 years, the economy doubles every 15 years. If history is a guide, the economy may transition within the next 60 years or so to a faster mode, with a doubling time of one to two years. Scientific progress may drive the current mode, while computer hardware may drive the next.
Democratic Failure Via Adverse Selection. first version July 1996.
Government intervention and other forms of collective choice (such as collective bargaining) have been widely recommended as cures for the "market-failure" of adverse selection and other forms of excessive-signaling or screening via separating-equilibria. This is because externally-imposed signal restrictions, such as signal-limits, signal taxes, or forced-pooling, can improve efficiency in simple signaling games.
Collective choices regarding restrictions are not, however, the same as restrictions imposed ex ante by a benevolent dictator. Voting on restrictions can, for example, allow informed participants to signal with their votes, resulting in a ``democratic failure'' of lower ex-ante efficiency relative to optimal ex-ante commitment. Insurance companies should be wary, for example, that unions representing riskier employees will vote to ask for more group-insurance.
With independent individual risks, however, asymptotic ex-ante efficiency results from collective choices made by random selfish juries. This is because fractionally-small juries who only know or care about their own types can at most signal only a small fraction of the relevant information. (see also a related dissertation proposal: Does Collective Choice Mitigate Adverse Selection?, March 1996.)
On Voter Incentives To Become Informed. first version June 1994, California Institute of Technology Social Science Working Paper No. 968, May 1996.
Before an election, two candidates choose policies which are lotteries over election-day distributive positions. I find conditions under which there exist mixed-strategy probabilistic-voting equilibria which are independent, treating voter groups independently. When voter efforts determine the quality of their signals regarding candidate positions, voters can have strong incentives regarding their visible efforts made before candidates choose policies. Also, scale economies in group information production can make voters prefer large groups. Even with zero information costs, however, voters can ex ante prefer ignorance to full information. Optimal ignorance emphasizes negative over positive news, and induces candidates to take stable positions.
Humanity seems to have a bright future, i.e., a non-trivial chance of expanding to fill the universe with lasting life. But the fact that space near us seems dead now tells us that any given piece of dead matter faces an astronomically low chance of begating such a future. There thus exists a great filter between death and expanding lasting life, and humanity faces the ominous question: how far along this filter are we?
Combining standard stories of biologists, astronomers, physicists, and social scientists would lead us to expect a much smaller filter than we observe. Thus one of these stories must be wrong. To find out who is wrong, and to inform our choices, we should study and reconsider all these areas. In particular we should seek evidence of extraterrestrials, such as via radio signals, Mars fossils, or dark matter astronomy. But contrary to common expectations, evidence of extraterrestrials is likely bad (though valuable) news. The easier it was for life to evolve to our stage, the bleaker our future chances probably are.