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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.The study uses a sample of all firms operating in 100 manufacturing industries to examine some aspects of firm dynamics. It finds that firm growth, the variability of firm growth, and the probability that a firm will fail decrease with firm age. It also finds that firm growth decreases at a diminishing rate with firm size even after controlling for the exit of slow-growing firms from the sample. Gibrat's Law therefbre fails although the severity of the failure decreases with firm size. I. INTRODUCTIONTHIs ARTICLE examines some dynamic aspects of firm behavior for all firms that operated in a sample of 100 manufacturing industries between 1976 and 1980. It examines the relationship between three aspects of industry dynamics-firm growth, firm dissolution, and the variability of firm growthand three key characteristics of a firm-its size, its age, and the number of plants it operates. It presents estimates of these relationships based on data pooled across all industries. It then presents a summary of the relationships found for each of the industries.A number of studies have examined the relationship between firm growth and firm size. Hart and Prais's [1956] pioneering study of the growth of British companies was followed by studies by Hymer and Pashigian [1962], Mansfield [1962], and Hall [1987] for the United States and Singh and Whittington [1975] and Kumar [1985] for the United Kingdom. This paper makes three contributions to this literature. First, it examines the relationship between firm age and firm dynamics. Except for my earlier paper [1987] and Brock and Evans [1986], previous studies have not examined the lifecycle aspects of firm growth. Second, it relies on a larger and more comprehensive sample of firms and reports results for more detailed industry groups than have previous studies. With the exception of Mansfield [1962], researchers have relied on samples of publicly * I would like to thank Timothy Bresnahan and Richard Schmalensee for helpful comments. DAVID S. EVANStraded (and therefore generally large) companies and have not disaggregated these samples below the 2-digit industry level. This paper uses data on the complete size distribution of firms in the manufacturing industries considered and summarizes results for separate 4-digit industries. Third, unlike previous studies except for Hall [1987] and myself, it controls for sample selection bias and heteroskedasticity. Little hinges, however, on the statistical novelties.The study finds several interesting relationships. First, firm growth decreases with firm size and firm age at the sample mean and for most of the firms in the interindustry sample. The negative relationship between growth and size holds for 89...

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[1] We show evidence that left-hand polarised electromagnetic ion cyclotron (EMIC) plasma waves can cause the loss of relativistic electrons into the atmosphere. Our unique set of ground and satellite observations shows coincident precipitation of ions with energies of tens of keV and of relativistic electrons into an isolated proton aurora. The coincident precipitation was produced by wave-particle interactions with EMIC waves near the plasmapause. The estimation of pitch angle diffusion coefficients supports that the observed EMIC waves caused coincident precipitation of both ions and relativistic electrons. This study clarifies that ions with energies of tens of keV affect the evolution of relativistic electrons in the radiation belts via cyclotron resonance with EMIC waves, an effect that was first theoretically predicted in the early 1970 0 s. Citation: Miyoshi,