Local martingales, arbitrage, and viability Free snacks and cheap thrills

Summary. We revisit a standard model of security prices as Ito processes, and provide some new economic insights about the role of arbitrage and credit limits within such a model. We show that the standard assumptions of a positive state prices and existence of an equivalent martingale measure exclude prices that are viable models of competitive equilibrium and that are potentially useful for modeling actual financial markets. These models have been dismissed in the past as allowing arbitrage, but in fact an agent who prefers more to less and who has limited access to credit may have an optimum. Received: June 9, 1999; revised version: October 4, 1999     

All grown up? The fate after 15 years of a quarter of a million UK firms born in 1998

The theory of firm growth is in a rather unsatisfactory state. However, the analysis of large firm-level datasets which have become available in recent years allows us to begin building an evidence base which can, in turn, be used to underpin the development of more satisfactory theory. Here we study the 239 thousand UK private sector firms born in 1998 over their first 15 years of life. A first, and quite striking, finding is the extraordinary force of mortality. By age 15, 90% of the UK firms born in 1998 are dead, and, for those surviving to age 15, the hazard of death is still about 10% a year. The chance of death is related to the size and growth of firms in an interesting way. Whilst the hazard rate after 15 years is largely independent of size at birth, it is strongly affected by the current (age 14) size. In particular, firms with more than five employees are half as likely to die in the next year as firms with less than five employees. A second important finding is that most firms, even those which survive to age 15, do not grow very much. By age 15 more than half the 26,000 survivors still have less than five jobs. In other words, the growth paths – what we call the ‘growth trajectories’ – of most of the 26,000 survivors are pretty flat. However, of the firms that do grow, firms born smaller grow faster than those born larger. Another striking finding is that growth is heavily concentrated in the first five years. Whilst growth does continue, even up to age 15, each year after age five it involves only a relatively small proportion of firms. Finally, there are two groups of survivors which contribute importantly to job creation. Some are those born relatively large (with more than 20 jobs) although their growth rate is quite modest. More striking though, is a very small group of firms born very small with less than five jobs (about 5% of all survivors) which contribute a substantial proportion (more than one third) of the jobs added to the cohort total by age 15.     

Endogenous trade bloc formation in an asymmetric world

This paper investigates how variations in endowments and the structure of preferences impact on the coalition formation decisions of asymmetric countries. There exist relatively few general results on the relationship between country characteristics and trade bloc formation. Here, new light is shed on this issue by systematically simulating bloc formation and by explicitly analysing the blocking behaviour of coalitions. A general equilibrium model of world trade is implemented with equilibrium coalition formation being modelled using the equilibrium concept of the core. It is found that global free trade is observed when all countries are similar. Customs unions tend to form between countries with ‘adjacent’ consumer preferences or with ‘adjacent’ endowments of their export commodity. Finally, in contrast to the existing literature but consistent with observed behaviour, it is found that free trade areas often Pareto dominate customs unions, provided consumer preferences differ sufficiently.     

The swing voter's curse with adversarial preferences

We analyze voting behavior in a large electorate in which voters have adversarial state-contingent preferences with incomplete information about the state of the world. We show that one type of voter can suffer from the swing voter's curse à la Feddersen and Pesendorfer [The swing voter's curse, Amer. Econ. Rev. 86 (1996) 408-424], and go on to characterize the symmetric Nash equilibria of this model under different parameter values. We prove that unlike settings with nonadversarial preferences, there are equilibria in which in one state of the world, a minority-preferred candidate almost surely wins the election and thus the election may fail to correctly aggregate information. Indeed, we show that the fraction of the electorate dissatisfied with the result can be as large as .     

The effects of state and Federal gun control laws on school shootings

School shootings are the highest profile type of murder in the United States. They are also the rarest type of murder. In 2014, there were only 17 firearm murders that were perpetrated in schools and colleges. The purpose of the present study is to determine the relationship between school shootings and state and Federal gun control laws. Using a Poisson, two-way fixed effects model, it was found that assault weapons bans reduced the number of school shooting victims by 54.4%. All other gun control laws (concealed carry laws, private sale background checks and Federal dealer background checks) had no statistically significant effects on school shootings. Although assault weapons bans may reduce the overall number of school shooting victims, the average reduction in murder victims may be less than 10 per year. Hence, it is unclear if gun control is the most appropriate policy to use to reduce the number school shooting victims.     

Dynamic Seemingly Unrelated Cointegrating Regressions

We propose the parametric Dynamic Seemingly Unrelated Regression (DSUR) estimator for simultaneous estimation of multiple cointegrating regressions. DSUR is efficient when the equilibrium errors are correlated across equations and is applicable for panel cointegration estimation in environments where the cross section is small relative to the available time series. We study the asymptotic and small sample properties of the DSUR estimator for both heterogeneous and homogeneous cointegrating vectors. We then apply the method to analyse two long-standing problems in international economics. Our first application revisits the estimation of long-run correlations between national investment and national saving. Our second application revisits the question of whether the forward exchange rate is an unbiased predictor of the future spot rate.     

Rational expectations for large CGE models: A practical algorithm and a policy application

We describe a simple iterative method for solving large dynamic CGE models under rational expectations. Details are given for Australia's MONASH model but the approach applies to a wide range of CGE models. The method is automated in the RunMONASH Windows software, putting CGE modelling under rational expectations within the reach of non-specialist modellers. We provide an illustrative application in which MONASH results under rational expectations are compared with results under static expectations. The application and supporting software can be downloaded. Results from the application are interpreted in terms of elementary economic mechanisms.     

The contracting value of tainted reports in cost reduction settings

While cost accounting is a well-developed discipline with a rich institutional past, it is criticized for being manipulable. This criticism is due, in part, to the existence of multiple, yet equally accepted cost allocation procedures or cost estimation techniques. Employing a principal-agent model, cost accounting is modeled as a menu of alternative methods which, conditional on agent effort, produce noisy, unbiased and independently distributed (i.e., equally defensible) measures from which a single realization is selected ex post as the report used to contract with the agent. Assuming that the report does not indicate which method produced it, the report modeled is “tainted” in that the lowest (most favorable to the agent) outcome is reported, where the “amount” of tainting corresponds to the menu's size. The paper identifies bright-line conditions where the principal's expected net payoff is independent of the amount of tainting, demonstrating that tainting does not necessarily affect the report's incentive value.