The credible identification of endogenous peer group effects---i.e. social multiplier or feedback effects---has long eluded social scientists. We argue that such effects are most credibly identified by a randomly assigned social program which operates at differing intensities within and between peer groups. The data we use are from Project STAR, a class size reduction experiment conducted in Tennessee elementary schools. In these data, classes were comprised of varying fractions of students who had previously been exposed to the Small class treatment, creating class groupings of varying experimentally induced quality. We use this variation in class group quality to estimate the spillover effect. We find that when allowance is made for this `feedback' effect of prior exposure to the Small class treatment, the peer effects account for much of the total experimental effects in the later grades, and the direct class size effects are rendered substantially smaller. JEL Classification: Z13, C51, C81, I21, C23 Keywords: Peer Effects; Data with a Group Structure; Organization of Schooling; Experimental Evidence 1

This paper analyzes the influence that juvenile offenders serving time in the same correctional facility have on each other’s subsequent criminal behavior. The analysis is based on data on over 8,000 individuals serving time in 169 juvenile correctional facilities during a two-year period in Florida. These data provide a complete record of past crimes, facility assignments, and arrests and adjudications in the year following release for each individual. To control for the non-random assignment to facilities, we include facility fixed effects, thereby estimating peer effects using only within-facility variation over time. We find strong evidence of peer effects for various categories of theft, burglary, and felony drug and weapon crimes; the influence of peers primarily affects individuals who already have some experience in a particular crime category. We also find evidence that peer effects are stronger in smaller facilities and that the predominant types of peer effects differ in residential versus non-residential facilities; effects in the latter are consistent with network formation among youth serving time close to home.

New ideas, products, and practices take time to diffuse, a fact that is often attributed to some form of heterogeneity among potential adopters. This paper examines three broad classes of diffusion models-- contagion, social influence, and social learning – and shows how to incorporate heterogeneity into each at a high level of generality without losing analytical tractability. Each type of model leaves a characteristic ‘footprint ’ on the shape of the adoption curve that provides a basis for discriminating empirically between them. The approach is illustrated using the classic study of Ryan and Gross on the diffusion of hybrid corn (JEL O33, D8, M3).

How we act, as well as how we are acted upon, are to a large extent influenced by our relatives, friends and acquaintances. This is true of which profession we decide to pursue, whether or not we adopt a new technology, as well as whether or not we catch the flu. In this chapter we provide an overview of research that examines how social structure impacts

How we act, as well as how we are acted upon, are to a large extent in‡uenced by our relatives, friends and acquaintances. This is true of which profession we decide to pursue, whether or not we adopt a new technology, as well as whether or not we catch the ‡u. In this chapter we provide an overview of research that examines how social structure impacts

1975. IFPRI is one of 15 agricultural research centers that receives its funding from governments, private foundations, and international and regional organizations, most of which are members of the Consultative Group on International Agricultural Research. “A 2020 Vision for Food, Agriculture, and the Environment ” is an initiative of the International Food Policy Research Institute (IFPRI) to develop a shared vision and a consensus for action on how to meet future world food needs while reducing poverty and protecting the environment. Through the 2020 Vision Initiative, IFPRI is bringing together divergent schools of thought on these issues, generating research, and identifying recommendations. This report was prepared for a policy consultation process coordinated by IFPRI and focused on the World’s Poor and Hungry People. IFPRI gratefully acknowledges the contributions of: Asian Development Bank (ADB) www.adb.org, Bill and Melinda Gates Foundation www.gatesfoundation.org, Canadian International Development Agency (CIDA) www.acdi-cida.gc.ca, Deutsche Welthungerhilfe (German Agro Action) www.

Security Considerations for the SHA-0 and SHA-1 Message-Digest Algorithms This document includes security considerations for the SHA-0 and SHA-1 message digest algorithm. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at

This study examines the factors that influence poor Indonesian households to invest in floating net aquaculture after being relocated due to a reservoir construction project. We take this relocation and introduction of a new technology as a natural experiment in order to identify the determinants of technology adoption. To compare three primary decision factors, social learning, risk attitudes, and credit accessibility, we analyze 16 year household panel data collected exclusively for this study. Our analysis reveals that credit accessibility is the most important factors that influence the rate of new technology investment. Also, social learning as well as risk attitude influence the investment decision significantly. Our results suggest that development projects that involve voluntary investments by the poor will be more successful if complementary services to promote credit and insurance accessibility and/or local information sharing are made available especially at the early phase.

www.ifpri.org IFPRI’s Discussion Papers contain preliminary material and research results. They have not been subject to formal review by IFPRI’s Publications Review Committee. They are circulated in order to stimulate discussion and critical comment.

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