spatial competition monopolistic competition and optimum product diversity abstract this is a republication of a passage from william vickrey s 1964 book microstatics which presents important results in spatial competition and monopolistic competition

cooperative and noncooperative r d in duopoly with spillovers contrary to the usual assumption made in most oligopoly models relations among firms are seldom of a wholly cooperative or noncooperative type in many situations they compete in some fields while they cooperate in others an important example is the case of cooperative research efforts bringing fierce competitors together two types of agreement are observed first r d cooperation can take place at the so called precompetitive stage companies share basic information and efforts in the r d stage but remain rivals in the market place 1 a second type of agreement involves an extended collusion between partners creating common policies at the product level the usual justifications of this extension are the difficulties of protecting intellectual property the idea is then to allow partners who have achieved inventions together to also control together the processes and products which embody the results of their collaboration in order to recuperate jointly their r d investments 2 what could be expected from these types of agreement is a reduction in r d expenditures because of less wasteful duplication and a reduction of total production because of more reprinted from the american economic review 78 5 1133 1137 1988 center for operations research econometrics 1348 louvain la neuve belgium we are grateful to jean

on the effects of downstream entry we study the effects of entry in a downstream market where firms e g compaq and ibm cvs and safeway buy an input e g microprocessor grocery items from an upstream supplier e g intel procter gamble and sell their output to consumers we show demand conditions where contrary to conventional wisdom entry of a new downstream firm lowers the downstream market output and increases the consumer price thus consumers may be better off with fewer sellers in such markets we also show that this entry may cause the profit of each incumbent downstream firm to i remain unchanged ii decrease or iii even increase also for a class of widely used demand conditions the supplier s optimal price is shown invariant to the entry exit of its downstream buyer firms we classify all possible effects of downstream entry in terms of fundamental market demand conditions

the flow approach to labor markets the flow approach to labor markets builds up from the flows of workers and of jobs it is based on three essential components a specification of labor demand in terms of flows of job creation destruction a process of matching between workers and firms and a process of wage determination where wages depend on the labor market prospects of employed workers and firms we think that this approach gives the right basic picture of unemployment and unemployment dynamics and of the relation between wage movements and the state of the labor market the additional richness it naturally delivers also captures important implications of labor market mechanisms for macroeconomics finally its structure is realistic enough to allow for a productive interaction with and use of micro work and micro evidence in both labor and product markets this paper shows the structure of the approach and some of its implications the first section develops a barebone model the second adds the flesh this abstract was borrowed from another version of this item

the determinants of equilibrium unemployment in britain a lot of energy is currently being expended in trying to understand what has been happening to unemployment in britain and the rest of the developed world in this paper we look at this question in the british context by trying to confront some possible explanations with the data since the data we use are quarterly over rather a short period we are setting the explanations a very hard test most explanations tend to be rather casual and the theories underpinning them ill developed thus for example the so called real wage argument is based on the idea that real wages affect labour demand and that the equilibrium real wage bears some relatively stable relationship to output per head but how stable is not clear thus whether or not we can expect a well defined stable ceteris paribus dynamic relationship between real product wages as a proportion of output per head and unemployment is equally unclear so if such a relationship does not show up in a quarterly regression model this may not be that serious for the theory nevertheless we must look for the relationship for how else are we ever to discriminate between a plethora of conflicting views the primary emphasis in this paper is on the secular factors affecting unemployment rather than the cyclical variables consequently we shall not be concerned with developing a coherent theory of cyclical fluctuations and in the empirical work we shall control for the cycle simply by making use of those exogenous or predetermined variables which other work in this field suggests are important 2 the remainder of the paper is set out as follows the next section is concerned with specifying a model which generates a definition of equilibrium unemployment the outline of this model is a pair of equations determining the flows into and out of unemployment and these are specified in section ii which looks closely at the possible variables involved section iii then deals with the results and presents some general conclusions

long run relationship between output capital labour and productivity in emerging market economies long run relationship between the variables involved in the production function is an issue that is important particularly in developing countries as the neoclassical production function is best suited for developed countries and its applicability to developing countries is questionable in various ways this motivates us to do this based on time series analysis taking indian textile industry as an example which is currently at its crucial stage as a critical industry in an emerging economy with the phasing out of multi fibre arrangement in 2005 this study documents existence of cointegration between capital and output negative impact of employment shocks on output changes substitutability between changes in capital and labour negative effect of shocks to changes in capital stock on productivity and negative effect of employment shocks on future productivity these results are in line with the general perceptions about this industry and with the standard neoclassical propositions as explained in t

multimarket competition theory and evidence the multimarket perspective identifies potential entrants as existing firms in related markets the paper uses this new framework to analyze entry strategies and entry deterrence successful entry permitting and entry deterring strategies require understanding of the feedbacks from the entry market to the home market and vice versa the multimarket perspective integrates literature on industrial organization and strategic management

multi market competition r d and welfare in oligopoly we investigate a multi market cournot model with strategic process research and development r d investments wherein a multi market firm meets new competitors that enter one of the markets we show that entry can enhance the total r d expenditures of the multi market firm moreover the incumbent s profit nonmonotonically changes as the number of entrants increases depending on the fixed entry costs and r d technologies both insufficient and excess entry can appear our results imply that diversification of their products can be a useful strategy for firms

buyers pricing behavior for risky alternatives encoding processes and preference reversals numerous studies have examined individuals minimum selling prices or certainty equivalents for lotteries as measures of preference but few have examined maximum buying prices because every transaction involves a buyer as well as a seller buyers pricing behavior is of interest in its own right two prospect theory based descriptive models of maximum buying prices the integration and segregation models are developed from different assumptions about cognitive encoding processes the models were tested experimentally using an incentive compatible cash payoff scheme in which maximum buying prices for bets and choices between bets were elicited from subjects surprisingly observed maximum buying prices were far below expected values even for bets with probabilities of winning near 1 0 this suggests buyers are strongly influenced by loss aversion and that the conventional assumption that the buying price for a risky alternative is a reduction in the alternative s payoffs fails to describe behavior instead it appears subjects predominately employed a segregation encoding process in which the buying price was encoded separately from the bet s payoffs and treated as a sure loss however an additional result was not explained adequately by either encoding model buying prices were less risk averse than choices for 3 expected value bets creating preference reversals of the standard kind lichtenstein and slovic 1971 but more risk averse for 100 expected value bets creating reverse preference reversals casey 1991 implications for the scale compatibility principle tversky et al 1988 are discussed two theoretical approaches are outlined which offer promise in the development of a unified model of price judgments and choice preferences under risk

prospect theory and market quality abstract we study equilibrium trading strategies and market quality in an economy in which speculators display preferences consistent with prospect theory kahneman and tversky 39 tversky and kahneman 63 i e loss aversion and mild risk seeking in losses loss aversion risk seeking in losses induces speculators to trade less more and less cautiously more aggressively with their private information but also makes them less more inclined to purchase private information when it is costly in order to mitigate enhance their perceived risk of a trading loss we demonstrate that these forces have novel nontrivial state dependent effects on equilibrium market liquidity price volatility trading volume market efficiency and information production

a model of competition between unemployed and employed job searchers an application to the unemployment outflow rate in britain this paper proposes a model to explain the allocation of new jobs to workers the central innovation is the analysis of the competition for jobs between employed and unemployed job searchers it is argued that the endogeneity of the fraction of the employed engaging in search is a crucial determinant of the unemployment outflow rate the model is applied to the unemployment outflow rate in britain the model fits the data well and encompasses its main rival copyright 1993 by royal economic society

price and variety in the spokes model the spokes model of nonlocalized spatial competition provides a new analytical tool for dierentiated oligopoly and a representation of spatial monopolistic competition an increase in the number of rms leads to lower equilibrium prices when consumers have relatively high product valuations but surprisingly to higher equilibrium prices for in termediate consumer valuations new entry alters consumer and social welfare through price market expansion and matching eects with free entry the market may pro vide too many or too few varieties from a social welfare perspective and the equilibrium price remains above marginal cost even when the number of rms is arbitrarily large

profit raising entry common wisdom suggests that entry reduces profits of incumbent firms on the contrary we demonstrate that if the incumbents differ in marginal costs and the entrants behave like stackelberg followers then entry may benefit the cost efficient incumbents while hurting the cost inefficient ones and the total outputs of all incumbents may be higher under entry

on the optimal design of lotteries is globally concave since thearguments against the plausibility of a convex utility function advanced in the previous sectionin relation to eu theory apply with equal force to the rdeu model by contrast as is shownbelow these arguments do not apply to risk seeking behavior associated with the possibility that

cooperative and noncooperative r d in an oligopoly with spillovers this paper examines the positive and normative effects of cooperative r d whereby member firms commit themselves to the joint profit maximizing level of r d in a precompetitive stage but remain fierce competitors in the product market vis a vis noncooperative r d socially first best r d and socially second best r d in the presence of sufficiently large r d spillovers neither noncooperative nor cooperative equilibria achieve even second best r d levels in the absence of spillover effects however while the cooperative r d level remains socially insufficient the noncooperative level may overshoot first and second best levels of r d copyright 1992 by american economic association

sectoral shifts and cyclical unemployment a substantial fraction of cyclical unemployment is better characterized as fluctuations of the frictional or natural rate than as deviations from some relatively stable natural rate shifts of employment demand between sectors of the economy necessitate continuous labor reallocation since it takes time for workers to find new jobs some unemployment is unavoidable this paper presents evidence that most of the unemployment fluctuations of the seventies unlike those in the sixties were induced by unusual structural shifts within the u s economy simple time series models of layoffs and unemployment are constructed that include a measure of structural shifts within the labor market these models are estimated and a derived natural rate series is constructed

free entry and social efficiency under vertical oligopoly we analyze a successive vertical oligopoly model that incorporates vertical relationships between industries and demonstrate that free entry in an industry that produces a homogeneous product can lead to a socially insufficient number of firms this is in contrast with the proevious findings that under cournot oligopoloy with fixed set up costs level of entry in the free entry equilibrium is socially excessive it has often been argued that this result can provide a justification for apparently anticompetitive entry regulations our finding yields an important policy implication that such a justification is not necessarily valid when vertical relationships ar taken into account

free entry and social inefficiency our goal is to provide a simple yet general exposition of the conditions under which the number of entrants in a free entry equilibrium is excessive insufficient or optimal our analysis compares the number of firms that enter a market when there is free entry with the number that would be desired by a social planner who is unable to control the behavior of firms once they are in the market that is we consider the second best problem of choosing the welfare maximizing number of firms while we take as given their noncompetitive behavior after entry we demonstrate that the crucial conditions for establishing the presence of an entry bias can be stated quite simply in terms of the outcome of the postentry game played by entrants in contrast to previous work we do not need to model this postentry game explicitly

market competition r d and firm profits in asymmetric oligopoly we investigate a cournot model with strategic r d investments wherein efficient low cost firms compete against less efficient high cost firms we findthat an increase in the number of high cost firms can stimulate r d by the low cost firms while it always reduces r d by the high cost firms more importantly this force can be strong enough to compensate for the loss that arises from more intense market competition the low cost firms profits may indeed increase with the number of high cost firms an implication of this result is far reaching as it gives low cost firms an incentive to help rather than harm high cost competitors we relate this implication to a practice known as open knowledge disclosure especially ford s strategy of disclosing its know how publicly and extensively at the beginning of the 20th century

innovation threats and strategic responses in oligopoly markets this paper deals with the strategic reaction of firms to competitive threats stemming from newly developed products of actual competitors product innovation projects go through multiple time consuming stages with several continuation termination decisions hence competitors can react to the threat before the new product is introduced and thereby may prevent or facilitate the product s introduction we consider a duopoly model where firm 1 can start a two stage product innovation project for obtaining a horizontally and vertically differentiated product in between the two stages firm 2 can react by making an investment that improves the competitive position of the current product we find that under weak vertical differentiation firm 2 wants firm 1 to innovate horizontal differentiation softens competition and firm 2 over invests to induce firm 1 to launch the new product second under strong vertical differentiation firm 1 starts the product innovation project triggering under investment by firm 2 but never finishes it the under investment makes firm 2 a weaker competitor which induces firm 1 not to innovate third under very strong vertical differentiation firm 2 prevents a launch of the new product by over investing this results in a strong competitive position of firm 2 it therefore captures such a big market share that firm 1 will not introduce the new product the situation of firm 1 in the old market has worsened the option to complete the innovation created by initiating the first stage of the innovation project has a negative value for firm 1

expo power utility a flexible form for absolute and relative risk aversion a new utility function which i call expo power is proposed that exhibits decreasing constant or increasing absolute risk aversion and decreasing or increasing relative risk aversion depending on parameter values numerical analysis suggests that the expo power function performs well in incorporating these risk preference structures and that arbitrary risk preference specifications may lead to biased risk response estimates

the effect of wage restraint on labour market flows the effects are studied of a wage restraint policy on flows in the labour market flows into and out of employment are distinguished and simple models are considered for these flows wage costs in particular are found to affect the flow of employment into unemployment which can be considered as a measure of job destruction but wage costs have no effect on the number of new hires which can be considered as a measure of job creation therefore wage moderation has preserved jobs that would otherwise have been destroyed the inflow of new hires is influenced by investments the generosity of the social benefit system and by structural mismatch apart from wage costs interest costs of firms also play a role in the job destruction process particularly since the beginning of the 1980s

heterogeneous agents and the implications of the markowitz model of utility for multi prize lottery tickets abstract the purpose in this letter is to demonstrate employing two parametric forms of the markowitz model of utility that heterogeneity of preferences of markowitz agents can contribute towards an explanation of why lotteries typically have multiple rather than single prizes

the existence of low end firms may help high end firms two models of competition between high end and low end products benefiting the high end firms are presented one is a quantity competition model and the other is a price competition model with product differentiation the key factor is the existence of two heterogeneous consumer groups those who demand only high end name brand products and those who care little whether products are high or low end we show that under certain conditions the profits of firms in the high end market are larger when there are firms producing low end products than when there are not the existence of price sensitive consumers who care little about product quality intensifies competition among the high end firms the existence of low end firms functions as a credible threat which induces the high end firms not to overproduce because price sensitive consumers buy products from the low end firms the result provides a new theoretical mechanism concerning the profitability and pricing of national brand firms after the entry of private labels it has an implication for pricing and marketing strategies established firms should not decrease their prices after the entry of nonestablished firms

a theory of anticipated utility abstract a new theory of cardinal utility with an associated set of axioms is presented it is a generalization of the von neumann morgenstern expected utility theory which permits the analysis of phenomena associated with the distortion of subjective probability

averting risk in the face of large losses bernoulli vs tversky and kahneman abstract prospect theory asserts that people display risk attraction in high probability losses but our subjects tend to avoid fair risks for large 30 to 90 high probability 80 real losses vindicating bernoulli s view that risk aversion is the dominant attitude

diversification versus optimality is there really a diversification puzzle abstractin this paper we provide a general valuation of the diversification attitude of investors first we empirically examine the diversification of mean variance optimal choices in the us stock market during the 11 year period 2003 2013 we then analyze the diversification problem from the perspective of risk averse investors and risk seeking investors second we prove that investors optimal choices will be similar if their utility functions are not too distant independent of their tolerance or aversion to risk finally we discuss investors attitude towards diversification when the choices available to investors depend on several parameters

prospect theory and mean variance analysis the experimental results of prospect theory pt reveal suggest that investors make decisions based on change of wealth rather than total wealth that preferences are s shaped with a risk seeking segment and that probabilities are subjectively distorted this article shows that while pt s findings are in sharp contradiction to the foundations of mean variance mv analysis counterintuitively when diversification between assets is allowed the mv and pt efficient sets almost coincide thus one can employ the mv optimization algorithm to construct ptefficient portfolios the markowitz 1952a tobin 1958 mean variance mv rule is probably the most popular investment decision rule under uncertainty in economics and in finance and it is widely employed by both academics and practitioners the strength of the mv analysis is that in the case of normal return distributions the choice of any expected utility maximizing risk averse individual will be according to the mv rule 1 the mv framework is the foundation of the sharpe 1964 lintner 1965 capital asset pricing model capm which is a cornerstone of modern finance moreover the mv framework provides a very important practical procedure for the construction of efficient portfolios while standard economic theory and in particular mv analysis assume expected utility maximization and risk aversion in a breakthrough article kahneman and tversky 1979 show that the actual behavior of individuals systematically and consistently violates these

entry barriers and economic welfare the relationship between economic welfare and the number of firms in a quasi cournot market is examined in the first place we presuppose the existence of a strong first best government that can enforce the marginal cost principle to the firms along with regulating the number of firms it is shown that there exist excessive number of firms at the free entry quasicournot equilibrium vis a vis the first best welfare maximizing number of firms the thrust of this result essentially survives even if we replace a utopian first best government by a secondbest government that leaves the firms to pursue their respective profit maximization freely and engages solely in regulating the number of firms it can be shown that the excess entry prevails again in this second best world recent studies in the theoretical industrial organization literature have uncovered several instances which cast serious doubt on the reasonableness of a widespread belief that increasing competition will increase welfare stiglitz 1981 p 184 it has been shown that there are cases which are not altogether unreasonable where social welfare will be increased by strengthening rather than weakening the protection of incumbent firms from the threat of potential entry this is in sharp contrast with the traditional belief 2 what is not known however is how robust these pathologies in fact are we intend to settle this problem by proving two excess entry theorems in the quasi cournot parametric conjectural variations homogeneous oligopoly model seade 1980a b in the first place we presuppose the existence of a strong first best government that could costlessly enforce the marginal cost pricing principle by firms in an oligopolistic market and regulate entry in pursuit of first best social welfare optimization it is shown that the number of firms at the free entry equilibrium exceeds the first best welfare optimizing number of firms the result has already been noted by von weizsacker 1980a b and others in terms of numerical examples our theorem 1 asserts that this phenomenon always holds true for the family of quasi cournot models at hand an implication of this result is that the existence of entry barriers which protect incumbent firms from potential competitors is not necessarily welfare decreasing in sharp contrast with the traditional belief a problem remains with theorem 1 however in that an omnipotent first best government does not exist in reality and the first best ideal is unrealizable in the actual economy therefore even if the intervention by a first best government with a view to restricting the number of firms within an industry may be welfare improving it does

a note on the excess entry theorem in spatial markets abstract vickrey vickrey w s 1964 microstatics harcourt brace and world new york shows that the number of firms entering is excessive in his circle model of product differentiation we broaden his result to a large class of transport and production cost functions in particular convex transport and production costs always entail excessive entry as long as a price equilibrium exists we also provide an example of insufficient entry in equilibrium

risk management strategies via minimax portfolio optimization recent extreme economic developments nearing a worst case scenario motivate further examination of minimax linear programming approaches for portfolio optimization risk measured as the worst case return is employed and a portfolio from maximizing returns subject to a risk threshold is constructed minimax model properties are developed and parametric analysis of the risk threshold connects this model to expected value along a continuum revealing an efficient frontier segmenting investors by risk preference divergence of minimax model results from expected value is quantified and a set of possible prior distributions expressing a degree of knightian uncertainty corresponding to risk preference determined the minimax model will maximize return with respect to one of these prior distributions providing valuable insight regarding an investor s risk attitude and decision behavior linear programming models for financial firms to assist individual investors to hedge against losses by buying insurance and a model for designing variable annuities are proposed

prospect theory much ado about nothing prospect theory is a paradigm challenging the expected utility paradigm one of the fundamental components of prospect theory is the s shaped value function the value function is mainly justified by experimental investigation of the certainty equivalents of prospects confined either to the negative or to the positive domain but not of mixed prospects which characterize most actual investments we conduct an experimental study withmixed prospects using for the first time recently developed investment criteria called prospect stochastic dominance psd and markowitz stochastic dominance msd we reject the s shaped value function showing thatat least 62 76 of the subjects cannot be characterized by such preferences we find support for the markowitz utility function which is a reversed s shaped function exactly the opposite of the prospect theory value function it is possible that the previous results supporting the s shaped value function are distorted because the prospects had only positive or only negative outcomes presenting hypothetical situations which individuals do not usually face and which are certainly not common in financial markets

dynamic portfolio choice and asset pricing with narrow framing and probability weighting this paper shows that the framework proposed by barberis and huang 2009 to incorporate narrow framing and loss aversion into dynamic models of portfolio choice and asset pricing can be extended to also account for probability weighting and for a value function that is convex on losses and concave on gains we show that the addition of probability weighting and a convex concave value function reinforces previous applications of narrow framing and cumulative prospect theory to understanding the stock market non participation puzzle and the equity premium puzzle moreover we show that a convex concave value function generates new wealth effects that are consistent with empirical observations on stock market participation

the shape of utility functions and organizational behavior based on measurements among 332 owner managers we investigate how theglobal shape of the utility function i e s shaped versus concave or convex over the total range of outcomes relates to choice behavior we find that the global shape of the utility function differs across decision makers about one third of the owner managers exhibit an s shaped utility function and that the global shape is linked to organizational behavior i e the production system employed a result that does not change when using different methods to identify the decision maker s global shape of the utility function the decision maker s risk attitude risk averse or risk seeking does not affect the choice of the production system whereas the degree of risk aversion based on thelocal shape of the utility function may be important in explaining owner managers trading behavior pennings and smidts 2000 more structural organizational behavior appears to be linked to theglobal shape of the utility function

choice under uncertainty evidence from ethiopia india and uganda we review experimental evidence collected from risky choice experiments using poor subjects in ethiopia india and uganda using these data we estimate that just over 50 of our sample behaves in accordance with expected utility theory and that the rest subjectively weight probability according to prospect theory our results show that inferences about risk aversion are robust to whichever model we adopt when we estimate each model separately however when we allow both models to explain portions of the data simultaneously we infer risk aversion for subjects behaving according to expected utility theory and risk seeking behaviour for subjects behaving according to prospect theory

the dynamics of job creation and destruction for university graduates why a rising unemployment rate can be misleading a large matched employer employee data set on the portuguese economy is used to analyse gross job creation and job destruction for university graduates compared to other groups of workers standard measures of gross job flows are computed and variance decomposition is used to check whether idiosyncratic shocks or aggregate and sectoral shocks can account for the time variation in gross job flows for schooling groups separately results indicate that the market for university graduates has expanded much more than that for undergraduates and that idiosyncratic shocks are more relevant driving job flows for university graduates than for nongraduates no support is therefore found for the pessimistic view that states that the expansion of higher education may have gone too far

welfare in differentiated oligopolies with more than two firms abstract excessive differentiation in the quality or location dimension in order to soften price competition is a well established conclusion concerning duopolistic markets this has inspired authors to discuss policy measures that may improve welfare in a differentiated market in the present paper a general welfare analysis is conducted for a varying number of firms it is shown that outcomes are almost optimal when three or more competitors are in the market in light of this a laissez faire policy should be adopted for a range of entry costs market outcomes entail insufficient entry therefore a subsidy to entry may improve welfare

the capabilities of new firms and the evolution of the us automobile industry firms that diversify into new and existing industries typically outperform de novo entrants but in some new industries diversifying firms are displaced by later entering de novo firms little is known about when and how new firms can overcome the advantages of diversifying firms this is investigated for one industry automobiles where new firms had considerable success all the entrants into the industry from its inception in 1895 through 1966 are identified the heritage of every entrant into the industry is traced including the founders of de novo entrants to explore how time of entry and pre entry experience affected firm survival while diversifying firms on average outperformed de novo entrants de novo entrants founded by individuals that worked for the leading automobile firms outperformed all firms and dominated the industry this is attributed to the novel organizational challenges faced by automobile firms which made the leading firms ideal training grounds for new entrants the implications of these findings for firm capabilities industry competition and regional economic development are discussed copyright 2002 oxford university press

social desirability of free entry a bilateral oligopoly analysis abstract this paper explores the social desirability of free entry by analyzing a bilateral oligopoly model with bargaining that incorporates the entry process of firms we demonstrate that free entry in an industry producing a homogeneous final product leads to a socially insufficient number of firms when the suppliers of the intermediate products have sufficiently strong bargaining power this is in contrast to previous findings in the theoretical industrial organization literature which demonstrate that in homogeneous final product markets with cournot oligopoly and fixed set up costs level of entry in the free entry equilibrium is always socially excessive our analysis yields an important policy implication given that the standard excess entry result has often been used as a justification for apparently anti competitive entry regulations

portfolio optimization with disutility based risk measure abstract in this paper we propose a quantile based risk measure which is defined using the modified loss distribution according to the decision maker s risk and loss aversion the properties related to different classes of disutility functions are established a portfolio selection model in the mean risk framework is proposed and equivalent formulations of the model generating the same efficient frontier are given the advantages of this approach are investigated using real world data from nyse the differences between the efficient frontier of the proposed model and the classical mean variance and mean cvar are quantified and interpreted extensive experiments show that the efficient portfolios obtained by using the proposed model exhibit lower risk levels and an increased satisfaction compared to the other two mean risk models

a note on the excess entry theorem in spatial models with elastic demand abstract this paper revisits the excess entry theorem in spatial models according to vickrey vickrey w s 1964 microstatics harcourt brace and world new york and salop salop s 1979 monopolistic competition with outside goods bell journal of economics 10 141 156 while relaxing the assumption of inelastic demand using a demand function with a constant demand elasticity we show that the number of firms that enter a market decreases with the degree of demand elasticity we find that the excess entry theorem does only hold when the demand elasticity is sufficiently small otherwise there is insufficient entry in the limiting case of unit elastic demand the market is monopolized we broaden our results with a more general transportation cost function

labour turnover in uk manufacturing a model of quits is constructed and combined with a labour demand function to produce a model of layoffs these are combined to provide an explanation of separations the main feature of this is the explicit incorporation of the interactions between quits and layoffs a linear approximation and a structural form are estimated on uk manufacturing data for 1965 82 it is shown that the most important determinant of separations is the state of demand in the labour market with some structural factors having a minor role to play