learning about a new technology pineapple in ghana this paper investigates the role of social learning in the diffusion of a new agri cultural technology in ghana we use unique data on farmers communication patterns to define each individual s information neighborhood conditional on many potentially confounding variables we find evidence that farmers adjust their inputs to align with those of their information neighbors who were surpris ingly successful in previous periods the relationship of these input adjustments to experience further indicates the presence of social learning in addition applying the same method to input choices for another crop of known technol ogy correctly indicates an absence of social learning effects jel d83 013 033 q16

ants rationality and recruitment this paper offers an explanation of behavior that puzzled entomologists and economists ants faced with two identical food sources were observed to concentrate more on one of these but after a period they would turn their attention to the other the same phenomenon has been observed in humans choosing between restaurants after discussing the nature of foraging and recruitment behavior in ants a simple model of stochastic recruitment is suggested this explains the herding and epidemics described in the literature on financial markets as corresponding to the equilibrium distribution of a stochastic process rather than to switching between multiple equilibria

consumer renewable energy technology adoption decision making comparing models on perceived attributes and attitudinal constructs in the case of solar water heaters in lebanon climate change and environmental problems are of major concern to governments organisations and consumers this stresses the need for a transition towards clean renewable energy systems to enable the diffusion of cleaner energy technology it is not enough to just have supportive policies in place the challenge is to ensure that consumers adopt them this article integrates insights from different research traditions into a research model to analyse consumers adoption decision making behaviour the innovation diffusion model by rogers was used and hypotheses from environmental psychological models were later added a survey was conducted among householders to assess the adoption of solar heating systems in the metn neighbourhood in lebanon n 200 the results revealed that adopters and non adopters differ significantly according to socio demographic factors such as income and household size the study confirmed the significance of typical variables of the diffusion of innovation model such as relative advantage observability independent judgment making and novelty seeking even when testing integrative analytical models furthermore the results indicate that by integrating hypotheses from environmental psychology models to the diffusion of innovation model a reasonable fit was achieved which is higher than the value of each model tested separately the results can be of use to policy makers the article ends with suggestions for future research

tests of a rational theory of the size of government in many countries the political party holding power changes more frequently than the trend growth rates in government spending and taxes shifts of political power are often preceded by rhetoric about meeting needs or cutting taxes which post election performances rarely match yet changes in the size of government up and down occur on average the size of government measured by the share of taxes or spending to output has increased in many countries during the past century but changes in size occur at diffrent rates and at times the relative size of government declines

word of mouth communication and percolation in social networks this paper develops a model of demand pricing and advertising in the presence of social learning via word of mouth communication between friends in the model consumers must receive information about a monopolist s product in order to consider purchasing it the presence of word of mouth is not sufficient for demand to be more elastic and prices to be lower compared to an informed population i derive the comparative static results of connectivity mean preserving spread of friendships and clustering of friends on prices the optimal targets for advertising are not generically the individuals with the most friends jel l12 l14 a fundamental issue for economists is understanding the process by which demand is formed through social learning by consumers this article develops a framework based on random graphs for understanding the ways social learning via

the transmission of sustainable harvesting norms when agents are conditionally cooperative experimental and observational studies have highlighted the importance of agents being conditionally cooperative when facing a social dilemma we formalize this mechanism in a theoretical model that portrays a small community having joint access to a common pool resource the diffusion of norms of cooperation takes place via interpersonal relations while individual agents face the temptation of higher profits by overexploiting the resource agents remain conditionally cooperative unless other individuals are misbehaving already we can observe a bubble of conditional cooperators slowly building up followed by a sudden burst which means that a transition from a cooperative social norm to non cooperation occurs interestingly in some parameter regions alternative stable states and limit cycles arise the latter implies that the same community goes through such a transition repeatedly over long time spans history thus repeats itself in the form of the creation and erosion of social capital

a new product growth for model consumer durables this article originally appeared in management science january 1969 volume 15 number 5 pp 215 227 published by the institute of management sciences a growth model for the timing of initial purchase of new products is developed and tested empirically against data for eleven consumer durables the basic assumption of the model is that the timing of a consumer s initial purchase is related to the number of previous buyers a behavioral rationale for the model is offered in terms of innovative and imitative behavior the model yields good predictions of the sales peak and the timing of the peak when applied to historical data a long range forecast is developed for the sales of color television sets

monopoly pricing and diffusion of social network goods abstract i present a model of dynamic pricing and diffusion of a network good sold by a monopolist in the model the network good is a subscription social network good this means that in each period each consumer has to pay a subscription price to use the good and the utility derived from subscribing to the good increases as more of her neighboring consumers subscribe consumers myopically optimize their subscription decisions and the monopolist chooses a sequence of subscription prices that maximizes his discounted sum of per period profits three main results emerge first i characterize a unique steady state of the monopoly market second i find that optimal sequences of subscription prices oscillate around the subscription price at the steady state third i analyze how changes in the monopolist s discount factor and the density of the social network affect the subscription price subscription rate and deadweight loss at the steady state

on the political economy of welfare expansion a comparative analysis of 18 advanced capitalist democracies 1960 1971 this article elaborates the thesis that economic growth and various types of collective action by class linked actors determine the expansion and decline of welfare spending in rich capitalist democracies our multivariate model of this thesis specified to 1960 1971 growth rates in direct cash transfer payments as proportions of gross domestic product is supported strongly by regression analyses these indicate that economic growth notably facilitates transfer payment growth they also suggest that rightist party participation in government notably dampens welfare expansion while leftist centrist and christian democratic party participation in government are conducive to welfare expansion and they suggest that the political influences of both unions and large industrial corporations are conducive to growth in transfers payments as well in addition state authorities appear to augment welfare spending in response to working class protests strike activity and capital investment disinvestment activ

adoption and diffusion of an innovation of uncertain profitability the argument has frequently been made that the pattern of diffusion associated with most new innovations will typically have certain characteristics a diffusion curve for an innovation is usually defined as the proportion of its potential users who have already adopted as a function of time measured from the first adoption many empirical studies by both economists and other social scientists have shown that diffusion curves nearly always have two distinct characteristics i they are s shaped the proportion adopted is an increasing function of time which is initially convex but eventually becomes concave and ii they tend to be right hand skewed the inflection point occurs at a time corresponding to a proportion adopted which is less than one half so that the function is concave over the greatest amount of time in fact this skewing is occasionally severe enough to make the diffusion curve appear concave everywhere the focus of most empirical studies of innovation diffusion has centered on identification of either the major determinants of the speed of diffusion or the characteristics of firms which determine how long they delay adoption the seminal contributions are griliches 6 study of hybrid corn and mansfield s 121 study of 12 industrial innovations these studies and most of the similar ones following conclude that diffusion is faster for innovations with higher profitability and that large firms tend to be the earliest adopters some studies e g mansfield 121 herregat 71 have attempted to ascertain

learning by doing and learning from others human capital and technical change in agriculture household level panel data from a nationally representative sample of rural indian households describing the adoption and profitability of high yielding seed varieties hyvs associated with the green revolution are used to test the implications of a model incorporating learning by doing and learning spillovers the estimates indicate that i imperfect knowledge about the management of the new seeds was a significant barrier to adoption ii this barrier diminished as farmer experience with the new technologies increased iii own experience and neighbors experience with hyvs significantly increased hyv profitability and iv farmers do not fully incorporate the village returns to learning in making adoption decisions

rules of thumb for social learning this paper studies agents who consider the experiences of their neighbors in deciding which of two technologies to use we analyze two learning environments one in which the same technology is optimal for all players and another in which each technology is better for some of them in both environments players use exogenously specified rules of thumb that ignore historical data but may incorporate a tendency to use the more popular technology in some cases these naive rules can lead to fairly efficient decisions in the long run but adjustment can be slow when a superior technology is first introduced

learning from neighbours when payoffs from different actions are unknown agents use their own past experience as well as the experience of their neighbours to guide their decision making in this paper we develop a general framework to study the relationship between the structure of these neighbourhoods and the process of social learning we show that in a connected society local learning ensures that all agents obtain the same payoffs in the long run thus if actions have different payoffs then all agents choose the same action and social conformism obtains we develop conditions on the distribution of prior beliefs the structure of neighbourhoods and the informativeness of actions under which this action is optimal in particular we identify a property of neighbourhood structures local independencewhich greatly facilitates social learning simulations of the model generate spatial and temporal patterns of adoption that are consistent with empirical work

word of mouth communication and social learning this paper studies the way that word of mouth communication aggregates the information of individual agents we find that the structure of the communication process determines whether all agents end up making identical choices with less communication making this conformity more likely despite the players naive decision rules and the stochastic decision environment word of mouth communication may lead all players to adopt the action that is on average superior these socially efficient outcomes tend to occur when each agent samples only a few others i introduction economic agents must often make decisions without knowing the costs and benefits of the possible choices given the frequency with which such situations arise it is understandable that agents often choose not to perform studies or experiments but instead rely on whatever information they have obtained via casual word of mouth communication reliance on this sort of easily obtained information appears to be common in circumstances ranging from consumers choosing restaurants or auto mechanics to business managers evaluating alternative organizational structures this paper studies two related environments in arguing that individuals reliance on word of mouth communication has interesting implications for their aggregate behavior first motivated by the diffusion of new technologies we consider a choice between two competing products with unequal qualities or payoffs and show that the structure of communication is important in determining whether the population as a whole is likely to learn to use the superior product second we consider a choice between two products or practices that are equally good and ask whether consumers are likely to herd onto a single choice or whether diversity will obtain even in the long run we explore the implications of word of mouth communication in a simple nonstrategic environment there is a large population of identical players each of whom repeatedly chooses between two possible actions each player s payoff is determined by his own

the causes of government expenditure growth a survey of the u s evidence abstract the growth of government budgets can be broken down into a institutional and institutional components the former component the familiar substitution income and population public goods tax sharing effects is estimated to contribute about two fifths of the growth of u s government spending the latter component rent seeking political redistributions bureaucracy and perceptual informational impedimentia is important too but an exact imputation cannot be asserted given the state of the art in empirical public choice theory the cross effects on spending of the growth of regulation and tax preferences or tax expenditures though interesting is not pursued

diffusion of behavior and equilibrium properties in network games situations in which agents choices depend on choices of those in close proximity be it social or geographic are ubiquitous selecting a new computer platform signing a political petition or even catching the flu are examples in which social interactions have a significant role while some behaviors or states propagate and explode within the population e g windows os the hiv virus others do not e g certain computer viruses our goal in this paper is twofold first we provide a general dynamic model in which agents choices depend on the underlying social network of connections second we show the usefulness of the model in determining when a given behavior expands within a population or disappears as a function of the environment s fundamentals we study a framework in which agents face a choice between two actions 0 and 1 e g whether to pursue a certain level of education switch to linux os etc agents are linked through a social network and an agent s payoffs from each action depend on the number of neighbors she has and her neighbors choices the diffusion process is defined so that at each period each agent best responds to the actions taken by her neighbors in the previous period assuming that her neighbors follow the population distribution of actions a mean field approximation steady states correspond to equilibria of the static game under some simple conditions equilibria take one of two forms some are stable so that a slight perturbation to any such equilibrium would lead the diffusion process to converge back to that equilibrium point other equilibria are unstable so that a slight change in the distribution of actions leads to a new distribution of actions and eventually to a stable steady state we call such equilibria tipping points we analyze how the environment s fundamentals cost distribution payoffs and network structure affect the set of equilibria and characterize the adoption patterns within the network the paper relates to recent work on network games and network diffusion including work by stephen morris 2000 pastor satorras and vespignani 2000 mark e j newman 2002 dunia lopez pintado 2004 jackson and brian w rogers 2007 jackson and yariv 2005 and andrea galeotti et al 2005 henceforth ggjvy its contribution is in characterizing diffusion of strategic behavior and analyzing the stability properties of equilibria and employing methods that allow us to make comparisons across general network structures and settings given that social networks differ substantially and systematically in structure across settings e g ethnic groups professions etc understanding the implications of social structure on diffusion is an important undertaking for a diverse set of applications

diffusion and cascading behavior in random networks abstract the spread of new ideas behaviors or technologies has been extensively studied using epidemic models here we consider a model of diffusion where the individuals behavior is the result of a strategic choice we study a simple coordination game with binary choice and give a condition for a new action to become widespread in a random network we also analyze the possible equilibria of this game and identify conditions for the coexistence of both strategies in large connected sets finally we look at how can firms use social networks to promote their goals with limited information our results differ strongly from the one derived with epidemic models and show that connectivity plays an ambiguous role while it allows the diffusion to spread when the network is highly connected the diffusion is also limited by high degree nodes which are very stable

minimum prices and social interactions evidence from the german renewable energy program minimum prices above the competitive level can lead to allocative inefficiencies we investigate whether this effect is more pronounced when decision makers are influenced by their social environment using data of minimum prices for renewable energy production in germany we test if individual decisions to install photovoltaic systems are affected by the investment decisions of others in the area we implement a propensity score matching routine on municipality level and estimate that existing panels in the municipality increase the probability and number of further installations considerably even in areas with minimal solar radiation thus social interaction can add secondary inefficiencies to the known allocative problems of minimum prices the social interaction effect is stronger in areas with more solar radiation and less unemployment a larger number of existing systems and more concentrated installations increase the social effect further

technological diffusion with social learning this paper attributes the slow diffusion of innovations to an informational externality in the adoption process the profitability of new technologies is uncertain but firing can learn progressively through observing the adoption experience of others given this prospect of social learning every firm would prefer that other firms adopt before it does in the absence of explicit coordination the firms could end up in a sequence of waiting contests this results in staggered adoptions even when all firms are ex ante identical the pace of diffusion is determined endogenously and shown to depend on the characteristics of the innovation copyright 1995 by blackwell publishing ltd

the size of government most research on the causes of growth in government expenditure has focused on the demand for government services in this paper we argue that in fact this growth may have occurred because of changes in supply changes in technology leading to increased specialization and thus increased opportunity costs of self production have led to increased market production and increased record keeping also female labor force participation has increased both of these factors serve to reduce the efficiency cost of collecting taxes if the demand for government spending has not changed this increase in supply would lead to a larger public sector we estimate a system of simultaneous equations for the period 1929 1970 incorporating this hypothesis and the results are consistent with the theory we are able to explain virtually all of the growth of government increases in female labor force participation seems to be a very important variable in this explanation

the growth of government in italy evidence from 1861 to 1979 that the public sector has grown both in absolute terms and relative to the rest of the economy is an undisputable fact that both growth rates have accelerated in recent history is also an unchallenged fact more cautious must we be about why these trends have occurred and are persisting we have tested three partially competing theories of government growth using italian annual data from 1861 to 1979 and assessed that the redistribution model explains the facts better than either the public goods model or the specialized interest hypothesis although the latter tells the most convincing story about the causes underlying transfers to firms we have also tried to discriminate between two competing views of a politician the value free intermediary found in the median voter literature and the entrepreneur emphasized in the theory of agency costs the bits of evidence we gathered are more consistent with a politician entrepreneur than a politician intermediary

chains of cooperation threshold effects in collective action granovetter s threshold model of collective action shows how each new participant triggers others until the chain reaction reaches a gap in the distribution of thresholds hence outcomes depend on the network of social ties that channel the chain reactions however structural analysis is encumbered by the assumption that thresholds derive from changing marginal returns on investments in public goods a learning theoretic specification imposes less stringent assumptions about the rationality of the actors and is much better suited to a structural analysis computer simulations suggest that threshold effects may be the key to solving the coordination problem when individual choices are contingent on participation by others this interdependence facilitates the coordination of contributions needed to shift the bistable system from a noncooperative equilibrium to a cooperative one further simulations with low density networks show that these chain reactions require bridges that link socially distant actors supporting granovetter s case for the strength of weak ties

innovation diffusion in heterogeneous populations contagion social influence and social learning 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 which provides a basis for discriminating empirically between them the approach is illustrated using the classic study of ryan and gross 1943 on the diffusion of hybrid corn

contagious cooperation temptation and ecosystem collapse real world observations suggest that social norms o f cooperation can be effective in overcoming social dilemmas such as the joint management of a c ommon pool resource but also that they can be subject to slow erosion and sudden collapse we show that these patterns of erosion and 15 collapse emerge endogenously in a model of a closed community harvesting a renewable natural resource in which individual agents face the tempta tion to overexploit the resource while a cooperative harvesting norm spreads through the community via interpersonal relations we analyze under what circumstances small changes in key parameters including the size of the community and the rate of technological progress trigger catastrophic transitions from 20 relatively high levels of cooperation to widespread norm violation causing the social ecological system to collapse

how powerful are public bureaucrats as voters empirical evidence is collected and discussed regarding the influence of public bureaucrats on government sector outcome in their capacity as consumer voters it is necessary to isolate the specific effect of working in the public sector compared to other occupations on voting participation and on the probability to support an increase in the public budget for a balanced evaluation of public bureaucrats power other forms of their influencing the government sector outcome need to be taken into account

partisan politics and public finance changes in public spending in the industrialized democracies 1955 1989 this paper evaluates the role that partisan politics plays in altering public spending levels the analysis covers over three decades of data on the developments of the public sectors in 16 oecd countries the results of the analysis lend firm support to the partisan politics model of special note is the distinction between the electorate and the government ideological preferences and the dominant role that the former plays the results also suggest contrary to conventional wisdom that partisan political influences have not been eliminated with the tightening of linkages to the international economy

contagion and uninvadability in local interaction games the bilingual game and general supermodular games abstract in a setting where an infinite population of players interact locally and repeatedly we study the impacts of payoff structures and network structures on contagion of a convention beyond 2 2 coordination games first we consider the bilingual game where each player chooses one of two conventions or adopts both i e chooses the bilingual option at an additional cost for this game we completely characterize when a convention spreads contagiously from a finite subset of players to the entire population in some network and conversely when a convention is never invaded by the other convention in any network we show that the pareto dominant risk dominant resp convention is contagious if the cost of bilingual option is low high resp furthermore if the cost is in a medium range both conventions are each contagious in respective networks and in particular the pareto dominant convention is contagious only in some non linear networks second we consider general supermodular games and compare networks in terms of their power of inducing contagion we show that if there is a weight preserving node identification from one network to another then the latter is more contagion inducing than the former in all supermodular games

why has the introduction of natural gas vehicles failed in germany lessons on the role of market failure in markets for alternative fuel vehicles despite private investments exceeding two billion euros and tax incentives of more than 500 million euros the market share of natural gas vehicles ngvs in germany has lagged far behind expectations and behind market developments in other countries with total cost of ownership being on average lower for ngvs than for gasoline and diesel vehicles this raises the question of the existence of market failure in the german ngv market we use a case study approach where we combine quantitative data with insights from a multi industry expert panel and in depth interviews with experts from industry government and civil society in order to examine whether and how different types of market failure contribute to the status quo in the german market for ngvs we conclude that coordination failure in complementary markets an artificially created monopoly of service stations at motorways imperfect information bounded consumer rationality and principle agent problems are the most prominent market failures inhibiting the development of a functioning market for ngvs our results are instructive for the design of effective public policies and investor strategies aiming to create markets for alternative fuel vehicles

models of technology diffusion abstract the literature on new technology diffusion is vast and it spills over many conventional disciplinary boundaries this paper surveys the literature by focusing on alternative explanations of the dominant stylized fact that the usage of new technologies over time typically follows an s curve the most commonly found model which is used to account for this model is the so called epidemic model which builds on the premise that what limits the speed of usage is the lack of information available about the new technology how to use it and what it does the leading alternate model is often called the probit model which follows from the premise that different firms with different goals and abilities are likely to want to adopt the new technology at different times in this model diffusion occurs as firms of different types gradually adopt it there are actually many ways to generate an s curve and the third class of models which we examine are models of density dependence popularized by population ecologists in these models the twin forces of legitimation and competition help to establish new technologies and then ultimately limit their take up finally we look at models in which the initial choice between different variants of the new technology affect the subsequent diffusion speed of the chosen technology such models often rely on information cascades which drive herd like adoption behaviour when a particular variant is finally selected

explaining the growth of government in sweden a disequilibrium approach previous studies aimed at explaining the growth of government in a particular country have failed to distinguish between explanatory variables acting on the supply and demand side respectively alternatively they have tested one explanation at a time implying explanatory equations that are misspecified in addition no allowance has been made for the fact that the interaction between supply and demand can hardly be assumed to be a self equilibrating process where the price of public goods and services adjusts to equate the two instead a framework of disequilibrium seems more appropriate for the analysis of the growth of government

consumer learning and hybrid vehicle adoption we study the effect of differences in product quality on new technology diffusion we propose a model in which heterogeneity in perceived product quality affects consumer adoption if consumers experientially infer the quality of a technology an increase in initial exposure to a low quality product may inhibit subsequent diffusion incentives intended to speed up adoption may in fact have the opposite effect if they propagate low quality signals we examine the predictions of the model using sales data for 11 hybrid vehicle models between 2000 and 2006 consistent with press reports that the first generation insight was perceived to be of lower quality than the first generation prius we find that conditional on overall hybrid vehicle adoption in the first 2 years locations with a relatively high prius market share experienced faster subsequent adoption than states with a relatively high insight market share we estimate the elasticity of new hybrid sales with respect to the prius penetration rate is 0 30 0 58 while the elasticity with respect to the insight penetration rate is 0 14 to 0 44

network structure and the diffusion of knowledge this paper models knowledge diffusion as a barter process in which agents exchange different types of knowledge this is intended to capture the observed practice of informal knowledge trading agents are located on a network and are directly connected with a small number of other agents agents repeatedly meet those with whom direct connections exist and trade if mutually profitable trades exist in this way knowledge diffuses throughout the economy we examine the relationship between network architecture and diffusion performance we consider the space of structures that fall between at one extreme a network in which every agent is connected to n nearest neighbours and at the other extreme a network with each agent being connected to on average n randomly chosen agents we find that the performance of the system exhibits clear small world properties in that the steady state level of average knowledge is maximal when the structure is a small world that is when most connections are local but roughly 10 percent of them are long distance the variance of knowledge levels among agents is maximal in the small world region whereas the coefficient of variation is minimal we explain these results as reflecting the dynamics of knowledge transmission as affected by the architecture of connections among agents

credibility and strategic learning in networks we analyze a model of diffusion in a fixed finite connected network there is an interested party that knows the quality of the product being propagated and chooses an implant in the network to influence other agents to buy agents are either innovators who adopt immediately or rational rational consumers buy if buying instead of waiting maximizes expected utility we consider the conditions on the network under which optimal diffusion of the good product with probability 1 is a perfect bayes equilibrium

interest groups and the size of government the results of the previous section estimates of a three equation model from 23 observations must obviously be regarded as tentative the consistent positive relationship between number of interest groups and size of government observed with changing sets of included independent variables changing samples of nations and treating the number of interest groups as either exogenous or codetermined does imply rather unequivocally that interest groups are able to influence public policies in such a manner as to lead to increased government size beyond helping to reinforce this conclusion the results of the previous section should be regarded as first steps in the development of a model of the polity that can explain participation in the political process by interest groups and citizens as well as the size of government

searching for leviathan an empirical study in several papers and a recent book geoffrey brennan and james buchanan 1977 1978 1980 have put forth a striking and controversial view of the public sector drawing by analogy on the conventional theory of monopoly in the private sector they envision a monolithic government that systematically seeks to exploit its citizenry through the maximization of the tax revenues that it extracts from the economy from this perspective they develop a fiscal constitution whose central purpose is to constrain leviathan by limiting in various ways its access to tax and other fiscal instruments while the leviathan hypothesis has been the source of lively debate and a wide range of policy proposals it has not been the subject of much systematic empirical work or testing this is a matter of some importance since the policy implications of the leviathan view are disturbing to put it mildly in particular brennan and buchanan virtually stand on their heads many of the basic theorems in public finance for an efficient and equitable tax system if in fact the leviathan view is an inaccurate depiction of the functioning of the public sector the introduction of their policy proposals is likely to make a sorry mess of the fiscal system the leviathan model does however have some straightforward implications for observable fiscal behavior it is the purpose of this paper to examine one of these testable implications brennan and buchanan stress that fiscal decentralization is itself a powerful constraint on leviathan competition among governments in the context of the interjurisdictional mobility of persons in pursuit of fiscal gains can offer partial or possibly complete substitutes for explicit fiscal constraints on the taxing power 1980 p 184 such competition among governments in a federal system that places heavy reliance on local fiscal decisions will greatly limit the capacity of leviathan to channel resources into the public sector in short as indicated by the epigraph to this paper the leviathan model implies that other things equal the size of the public sector should vary inversely with the extent of fiscal decentralization 2