We exploit differences in early colonial experience to estimate the effect of institutions on economic performance. Our argument is that Europeans adopted very different colonization policies in different colonies, with different associated institutions. The choice of colonization strategy was, at least in part, determined by the feasibility of whether Europeans could settle in the colony. In places where Europeans faced high mortality rates, they could not settle and they were more likely to set up worse (extractive) institutions. These early institutions persisted to the present. We document these hypotheses in the data. Exploiting differences in mortality rates faced by soldiers, bishops and sailors in the colonies during the 18th and 19th centuries as an instrument for current institutions, we estimate large effects of institutions on income per capita. Our estimates imply that a change from the worst (Zaire) to the best (US or New Zealand) institutions in our sample would be associated with a five fold increase in income per capita.

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Requirements analysis includes a preliminary acquisition step where a global model for the specification of the system and its environment is elaborated. This model, called requirements model, involves concepts that are currently not supported by existing formal specification languages, such as goals to be achieved, agents to be assigned, alternatives to be negotiated, etc. The paper presents an approach to requirements acquisition which is driven by such higher-level concepts. Requirements models are acquired as instances of a conceptual meta-model. The latter can be represented as a graph where each node captures an abstraction such as, e.g., goal, action, agent, entity, or event, and where the edges capture semantic links between such abstractions. Well-formedness properties on nodes and links constrain their instances - that is, elements of requirements models. Requirements acquisition processes then correspond to particular ways of traversing the meta-model graph to acquire approp...

In this article we offer guidelines for the determination of key sizes for symmetric cryptosystems, RSA, and discrete logarithm based cryptosystems both over finite fields and over groups of elliptic curves over prime fields. Our recommendations are based on a set of explicitly formulated parameter settings, combined with existing data points about the cryptosystems.

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We investigate whether civil wars have economic causes. The model is based on utility theory, rebels will conduct a civil war if the perceived benefits outweigh the costs of rebellion. Using probit and tobit models the propositions are tested empirically. Four variables, initial income, ethno-linguistic fractionalisation, the amount of natural resources, and initial population size are significant and strong determinants of the duration and the probability of civil wars. One important finding is that the relationship between civil wars and ethnic diversity is non-monotonic; highly fractionalised societies have no greater risk of experiencing a civil war than homogenous ones.

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Community is a core construct in social thought. Its intellectual history is lengthy and abundant. Community was a prominent concern of the great social theorists, scientists, and philosophers of the nineteenth and early twentieth centuries (e.g., Dewey 1927; Durkheim [1893] 1933;

ABSTRACT An influential conventional wisdom holds that civil wars proliferated rapidly with the end of the Cold War and that the root cause of many or most of these has been ethnic nationalism. We show that the current prevalence of internal war is mainly the result of a steady accumulation of protracted conflicts since the 50s and 60s rather than a sudden change associated with a new, post-Cold War international system. We also find that after controlling for per capita income, more ethnically or religiously diverse countries have been no more likely to experience significant civil violence in this period. We argue for understanding civil war in this period in terms of insurgency or rural guerrilla warfare, a particular form of military practice that can be harnessed to diverse political agendas, including but not limited to ethnic nationalism. The factors that explain which countries have been at risk for civil war are not their ethnic or religious characteristics but rather the conditions that favor insurgency. These include poverty, which marks financially and bureaucratically weak states and also favors rebel recruitment, political instability, rough terrain, and large populations. * James D. Fearon and David D. Laitin are Professors of Political Science, Stanford University, Stanford, CA, 94305-6044. We wish to thank the many people who provided comments on an earlier versions of this paper in a series of seminar presentations. The authors also gratefully acknowledge the support of the National Science Foundation (grants SES-9876477 and SES-9876530); support from the Center for Advanced Study in the Behavioral Sciences with funds from the William and Flora Hewlett Foundation; valuable research assistance from Ebru Erdem, Nikolay Marinov, Quinn Mecham, David Patel, and TQ Shang; and Paul Collier for sharing some of his data. Between 1945 and 1999, about 3.33 million battle deaths occurred in the 25 interstate wars that killed at least 1000 and had at least 100 dead on each side. These wars involved just 25 states that suffered casualties of at least 1000, and had a median duration of not quite 3 months. By contrast, in the same period there were roughly 122 civil wars that killed at least 1000. A conservative estimate of the total dead as a direct result of these conflicts is 16.2 million, five times the interstate toll. These civil wars occurred in 73 states -more than a third of the United Nations system -and had a median duration of roughly six years.

There are many cases in the literature in which reuse of the same key material for different functions can open up security holes. In this paper, we discuss such interactions between protocols, and present a new attack, called the chosen protocol attack, in which an attacker may write a new protocol using the same key material as a target protocol, which is individually very strong, but which interacts with the target protocol in a security-relevant way. We finish with a brief discussion of design principles to resist this class of attack.