learning to believe in sunspots a number of authors have shown that competitive economies may possess sunspot equilibria that is rational expectations equilibria in which purely extrinsic uncertainty affects equilibrium prices and allocations 2 such results demonstrate that it does not require a lack of faith in the rationality of market participants to believe that competitive markets may be subject to purely speculative fluctuations driven solely by expectations 3 the mere existence of sunspot equilibria as solutions to a system of marketclearing conditions however might not be judged sufficient to indicate that competitive markets with rational participants could ever be subject to speculative instability the sunspot equilibria represent states of affairs in which agents act differently in the case of different realizations of the sunspot variable and it is rational for each agent to do so but it might be thought unlikely that the beliefs of all the participants in the market could ever come to be coordinated so as to bring about an equilibrium of that kind it is rational to believe that sunspots convey information about future states of affairs once the economy is in a sunspot equilibrium but why would rational agents ever begin to believe in such a thing so as to create the conditions under which the belief is rational in order to address such a question one must go beyond the mere statement of the conditions for equilibrium and discussion of what states of affairs satisfy them one must specify an explicit dynamic process according to which the beliefs of agents adjust when out of equilibrium any exercise of this kind is necessarily unsatisfactory as there is no univocal meaning for the postulate of rational behavior outside of an equilibrium it may well be the case that

animal spirits and credit cycles in this paper we extend the behavioral macroeconomic model as proposed by de grauwe 2012 to include a banking sector the behavioral model takes the view that agents have limited cognitive abilities as a result it is rational to use simple forecasting rules and to subject the use of these rules to a fitness test agents are then driven to select the rule that performs best the behavioral model produces endogenous and self fulfilling movements of optimism and pessimism animal spirits our main result is that the existence of banks intensifies these movements creating a greater scope for booms and busts thus banks do not create but amplify animal spirits we find that increases in the equity ratios of banks tend to reduce the importance of animal spirits over the business cycle the other policy conclusion we derive from our results is that the central bank has an important responsibility for stabilising output output stabilization is an instrument to tame the animal spirits this has the effect of improving the trade off between inflation and output volatility

ppp exchange rate rules macroeconomic in stability and learning in order to maintain competitiveness governments in developing economies seem to have pursued purchasing power parity ppp exchange rate rules by adjusting the nominal devaluation rate in response to real exchange rate deviations from an intermediate target this article shows that these rules are likely to induce macroeconomic instability as they generate sunspot driven fluctuations that are in fact learnable by agents in the expectational stability sense it finds that the existence of these learnable sunspots depends among others on open economy features including the degree of openness and the degree of exchange rate pass through to consumer s import prices

dynamic predictor selection in a new keynesian model with heterogeneous expectations abstract this paper introduces dynamic predictor selection into a new keynesian model with heterogeneous expectations and examines its implications for monetary policy we extend branch and mcgough 2009 by incorporating endogenous time varying predictor proportions along the lines of brock and hommes 1997 we find that periodic orbits and complex dynamics may arise even if the model under rational expectations has a unique stationary solution the qualitative nature of the non linear dynamics turns on the interaction between hawkishness of the government s policy and the extrapolative behavior of non rational agents

optimal constrained interest rate rules we show that if policymakers compute the optimal unconstrained interest rate rule within a taylor type class they may be led to rules that generate indeterminacy and or instability under learning this problem is compounded by uncertainty about structural parameters since an optimal rule that is determinate and stable under learning for one calibration may be indeterminate or unstable under learning under a different calibration we advocate a procedure in which policymakers restrict attention to rules constrained to lie in the determinate learnable region for all plausible calibrations and that minimize the expected loss computed using structural parameter priors subject to this constraint

rescaling contraction with a lower cost technology when revenue declines abstract a mature oil field rescaled contraction describes a switch to a technological alternative more appropriate for the depleted state of an underlying resource off shore oil rigs are an illustration since the original technological scale designed for very large output flows becomes inappropriate as the operational efficiency declines later in life and facing a dwindling output flow so a more appropriate extraction technology becomes economic a real option representation is formulated on a stochastic oil price and deteriorating output volume we consider investment divestment decisions both separately and jointly which have different implications for government policies and also option values the resulting model yields analytical or semi analytical results indicating that immediate switching to the lower cost technology could sometimes be hastened as the price volatility increases depending on the current revenue if divestment and switching are considered jointly however greater volatility could also promote hysteresis

effects of brand preference product attributes and marketing mix variables in technology product markets we develop a demand model for technology products that captures the effect of changes in the portfolio of models offered by a brand as well as the influence of the dynamics in its intrinsic preference on that brand s performance to account for the potential correlation in the preferences of models offered by a particular brand we use a nested logit model with the brand e g sony at the upper level and its various models e g mavica fd dsc etc at the lower level of the nest relative model preferences are captured via their attributes and prices we allow for heterogeneity across consumers in their preferences for these attributes and in their price sensitivities in addition to heterogeneity in consumers intrinsic brand preferences together with the nested logit assumption this allows for a flexible substitution pattern across models at the aggregate level the attractiveness of a brand s product line changes over time with entry and exit of new models and with changes in attribute and price levels to allow for time varying intrinsic brand preferences we use a state space model based on the kalman filter which captures the influence of marketing actions such as brand level advertising on the dynamics of intrinsic brand preferences hence the proposed model accounts for the effects of brand preferences model attributes and marketing mix variables on consumer choice first we carry out a simulation study to ensure that our estimation procedure is able to recover the true parameters generating the data then we estimate our model parameters on data for the u s digital camera market overall we find that the effect of dynamics in the intrinsic brand preference is greater than the corresponding effect of the dynamics in the brand s product line attractiveness assuming plausible profit margins we evaluate the effect of increasing the advertising expenditures for the largest and the smallest brands in this category and find that these brands can increase their profitability by increasing their advertising expenditures we also analyze the impact of modifying a camera model s attributes on its profits such an analysis could potentially be used to evaluate if product development efforts would be profitable

the valuation of sequential exchange opportunities sequential exchange opportunities are valued using the techniques of modern option pricing theory the vehicle for analysis is the concept of a compound exchange option this security is shown to exist implicitly in several contractual settings a valuation formula for this option is derived the formula is shown to generalize much previous work in option pricing several applications of the formula are presented

stable near rational sunspot equilibria abstract we introduce a new class of solutions to nonlinear forward looking models called near rational sunspot equilibria nrse nrse are natural nonlinear extensions of the usual sunspot equilibria associated with the linearized version of the economy and are near rational in that agents use the optimal linear forecasting model when forming expectations generic results for existence and stability under learning are established nrse in indeterminate nonlinear models are found to be stable under learning provided that the corresponding linearized model s minimal state variable solution is e stable nrse are readily computable and our results make it possible to use the standard linear tools to search for stable nrse we illustrate our results using a canonical nonlinear new keynesian model

heterogeneous expectations adaptive learning and evolutionary dynamics this paper presents a linear self referential macroeconomic model with the possibility of multiple equilibria where agents have the choice of using one of two forecasting models one of minimum state variable form and the other of sunspot form to form expectations of current and future prices endogenous predictor selection is modeled as an evolutionary game where individuals choose among the forecasting models based on relative performance some nash solutions are not relevant as they are not stable under evolutionary or adaptive learning finally it is shown that the sunspot equilibrium is fragile against temporary shocks to information costs

investment in technological innovations an option pricing approach abstract this paper develops a model of the optimal investment strategy for a firm confronted with a sequence of technological innovations we incorporate many of the most important characteristics of real world technology markets for example we permit innovations to be stochastic in their arrival times and their profitability we also incorporate learning so that firms adopting current innovations become better able to benefit from future innovations the model yields four distinct investment strategies the model is then used to predict actual firm policy these implications are discussed and compared with observed firm behavior

expectations and the stability problem for optimal monetary policies eine auf den fundamentaldaten beruhende regelbindung der geldpolitik ohne selbstverpflichtung die bei vollkommen rationalen erwartungen der privaten akteure optimal ware ist instabil wenn diese akteure de facto den ublichen regeln des adaptiven lernens folgen dieses problem lasst sich dadurch beheben dass die erwartungen privater akteure berucksichtigt und in geeigneter weise in die optimale geldpolitik einbezogen werden diese eindeutige schlusfolgerung gilt auch dann wenn sich der geldpolitische entscheidungstrager und die privaten akteure in einem simultanen lernprozess befinden unsere ergebnisse zeigen wie wichtig es ist die geldpolitik angemessen zu gestalten und dabei nicht nur die fundamentaldaten sondern auch direkt die beobachteten erwartungen privater haushalte und unternehmen zu berucksichtigen

investment interest rate policy and equilibrium stability abstract carlstrom and fuerst 2005 investment and interest rate policy a discrete time analysis journal of economic theory 123 4 20 show that in the presence of investment activity and price stickiness indeterminacy of equilibrium is induced by forward looking monetary policy that sets the interest rate in response only to future inflation in a stochastic version of their model we find that this indeterminacy problem is due to a cost channel of monetary policy whereby inflation expectations become self fulfilling and the problem can be overcome once the forward looking policy responds also to current output or contains sufficiently strong interest rate smoothing since this prevents the self fulfilling expectations we also show that when e stability is adopted as the selection criterion from multiple equilibria even the forward looking policy generates a locally unique non explosive e stable fundamental rational expectations equilibrium as long as the policy response to expected future inflation is sufficiently strong

adaptive learning and distributional dynamics in an incomplete markets model abstract recent research shows that several dsge models provide a closer fit to the data under adaptive learning this paper extends this research by introducing adaptive learning in the model of krusell and smith 1998 with uninsurable idiosyncratic risks and aggregate uncertainty a first contribution of this paper establishes that the equilibrium of this framework is stable under least squares learning the second contribution consists of showing that bounded rationality enhances the ability of this model to match the distribution of income in the us learning increases significantly the gini coefficients because of the opposite effects on consumption of the capital rich and of the capital poor agent the third contribution is an empirical exercise that shows that learning can account for increases in the income gini coefficient of up to 25 in a period of 28 years overall these findings suggest that adaptive learning has important distributional repercussions in this class of models

learning monetary policy and asset prices this working paper should not be reported as representing the view s of the imf the views expressed in this working paper are those of the author s and do not necessarily represent those of the imf or imf policy working papers describe research in progress by the author s and are published to elicit comments and to further debate

e stability vis a vis determinacy in regime switching models abstract this paper examines e stability determinacy and indeterminacy in a general class of regime switching models with lagged endogenous variables using determinacy conditions from cho 2016 2020 our first result extends mccallum 2007 to models with time varying parameters the unique mean square stable equilibrium is e stable if agents have current information and one period ahead decision rules further we address the existence of e stable non fundamental equilibria and find that iteratively e stable equilibria of indeterminate switching models can exist finally we show that indeterminate new keynesian models with persistent recurring interest rate peg regimes admit iteratively e stable equilibria in special cases the iterative e stability condition coincides with the long run taylor principle

learning about monetary policy rules abstract we study macroeconomic systems with forward looking private sector agents and a monetary authority that is trying to control the economy through the use of a linear policy feedback rule we use stability under recursive learning a la evans and honkapohja learning and expectations in macroeconomics princeton university press princeton new jersey 2001 as a criterion for evaluating monetary policy rules in this context we find that considering learning can alter the evaluation of alternative policy rules

renewing assets with uncertain revenues and operating costs we study optimal replacement and abandonment decisions for real assets when both revenues and costs are uncertain and deteriorate with age we develop an implicit representation of the renewal boundary as the solution to a set of simultaneous equations this quasi analytical method has the merit of computational ease and transparency we show that the correlation between revenues and operating costs has a significant influence on the renewal boundary and that the increase in revenue immediately following a renewal has a greater relative influence on the boundary than either operating cost or renewal cost the quasi analytical method is sufficiently flexible to deal with other real option models involving 2 variables

asset retirement with infinitely repeated alternative replacements harvest age and species choice in forestry abstract at what age should productive assets be retired how should replacements be chosen when they differ in their uncertain ability to generate future incomes as a particular version of that problem we study the tree harvesting decision with two possible replacement species whose values as timber are stochastic and whose growth functions are deterministic in the single rotation wicksell problem starting with a bare piece of land an empty shop it is optimal to choose and plant one species immediately if its current value is sufficiently high relative to that of the other species the alternative equipment however if the species are insufficiently price differentiated it is preferable to leave the land vacant the shop empty despite the opportunity cost of doing so in the repeated version of the problem it is never optimal to leave the land bare provided the cost of replacement is null furthermore the optimal harvest tree retirement age not only depends on the price and current productivity of the trees in place but also on the price and productivity of the other species because it may replace the current one the harvest age reaches a peak at some critical threshold of the relative price that signals the necessity to switch to the alternative species indeed this is when the opportunity cost of choosing one alternative replacement over the other is the highest the land value and also the value of the firm is similar to an american option with free boundary infinite expiry period and endogenous payoff the paper highlights the opportunity cost of alternative replacement options and the central role of their volatility in both asset retirement and replacement choice decisions all results are derived analytically a numerical treatment by the penalty method completes the resolution

on non uniqueness in rational expectations models an attempt at perspective abstract many macroeconomic models involving rational expectations give rise to an infinity of solution paths even when the models are linear in all variables some writers have suggested that this non uniqueness constitutes a serious weakness for the rational expectations hypothesis one purpose of the present paper is to argue that the non uniqueness in question is not properly attributable to the rationality hypothesis but instead is a general feature of dynamic models involving expectations it is also argued that there typically exists in a very wide class of linear rational expectations models a single solution that excludes bubble or bootstrap effects one that occur only because they are arbitrarily expected to occur a systematic procedure for obtaining solutions free from such effects is introduced and discussed in addition this procedure is used to interpret and reconsider several prominent examples with solution multiplicities including ones developed by fischer black and john b taylor

expectational stability of sunspot equilibria in non convex economies we examine the stability under learning e stability of sunspot equilibria in non convex real business cycle models the production technology is cobbdouglas with externalities generated by factor inputs we establish that with a general utility function the well known benhabib farmer condition benhabib and farmer 1994 that the labor demand curve is upward sloping and steeper than the frisch labor supply curve is necessary for joint indeterminacy and e stability then with a separable utility function and allowing for negative externalities from capital inputs we discover large regions in parameter space corresponding to stable indeterminacy that is learnable sunspot equilibria these existence results overturn the conventional wisdom that sunspot equilibria in rbc type models are inherently unstable and provide concise closure to the stability puzzle of evans and mcgough 2005b

e equilibria and adaptive expectations output and inflation in the lbs model abstract this paper examines issues of convergence the variability of the dynamic paths and end value outcomes of output and inflation in the london business school lbs macromodel where adaptive learning schemes are used to form expectations of future variables first we examine the sensitivity of the outcomes from an exogenous oil price shock to alternative formulations of the adaptive expectations scheme the results suggest that convergence is not certain for ad hoc specifications of the expectations rule but that where solutions do exist for a range of empirically estimated rules the results show a sufficient degree of similarity particularly for output to suggest more than weak possibly strong e stability nonetheless the dynamic paths for output and inflation differ significantly we then focus on one simple expectations rule and test the variability of model outcomes when the associated hyperparameters differ in some cases this leads to no convergence but where a stable region is found the output and inflation results differ markedly both for the dynamics and for the end values therefore the speed of learning as well as the expectations rule matters for the output and inflation paths

inflation forecasts and monetary policy proposals for inflation targeting as a strategy for monetary policy leave open the important operational question of how to determine whether current policies are consistent with the long run inflation target an interesting possibility is that the central bank might target current private sector forecasts of inflation either those made explicitly by professional forecasters or those implicit in asset prices we address the issue of existence and uniqueness of rational expectations equilibria when the central bank uses private sector forecasts as a guide to policy actions in a dynamic model which incorporates both sluggish price adjustment and shocks to aggregate demand and aggregate supply we show that strict targeting of inflation forecasts is typically inconsistent with the existence of rational expectations equilibrium and that policies approximating strict inflation forecast targeting are likely to have undesirable properties we also show that economies with more general forecast based policy rules are particularly susceptible to indeterminacy of rational expectations equilibria we conclude that although private sector forecasts may contain information useful to the central bank ultimately the monetary authorities must rely on an explicit structural model of the economy to guide their policy decisions this abstract was borrowed from another version of this item this abstract was borrowed from another version of this item

learning about monetary policy rules when labor market search and matching frictions matter abstract this paper examines the implications of labor market search and matching frictions for determinacy and e stability of rational expectations equilibrium ree in a sticky price model with interest rate policy when labor adjustment takes place solely at the extensive margin forecast based policy that meets the taylor principle is likely to induce indeterminacy and e instability regardless of whether it is strictly or flexibly inflation targeting when labor adjustment takes place at both the extensive and intensive margins the strictly inflation forecast targeting policy remains likely to induce indeterminacy but it generates a unique e stable fundamental ree as long as the taylor principle is satisfied therefore the presence of search and matching frictions changes the determinacy properties of a strictly inflation forecast targeting policy and alters its e stability properties when only an extensive margin is present but not when labor adjustment takes place at both margins

good timing the economics of optimal stopping abstract this paper presents an economic interpretation of the optimal stopping of perpetual project opportunities under both certainty and uncertainty prior to stopping the expected rate of return from delay exceeds the rate of interest the expected rate of return from delay is the sum of the expected rate of change in project value and the expected rate of change in the option premium associated with waiting at stopping the expected rate of return from delay has fallen to the rate of interest viewing stopping in this way unifies the theoretical and practical insights of the theory of stopping under certainty and uncertainty

the net present value method versus the option value of waiting a note on farzin huisman and kort 1998 abstract using the tools of real options theory farzin huisman and kort 1998 investigate the optimal timing of technology adoption in a model in which there is ongoing technological progress and the firm s investment decision is irreversible when the firm can switch technologies n farzin et al 1998 obtain the surprising result that the criterion for adopting a new technology derived from real options theory coincides with the net present value criterion for all but the last switch this note points out a mistake in farzin et al s 1998 derivations that leads to the above result we show that compared to the net present value approach the firm will defer the adoption of a new technology when it takes the option value of waiting into account

an exploration of the eductive justifications of the rational expectations hypothesis this paper examines justifications of the rational expectations hypothesis that rely on the analysis of the agents mental forecasting educing activity which involves forecasting the forecasts of others etc the corresponding concept of eductive learning stability based on the game theoretical concept of rationalizability is primarily used within the classical muth model conditions for coordination of beliefs are interpreted and discussed they are robust to the introduction of noise more generally eductive stability fits economic intuition on coordination stability increases when the industry product differentiation increases and when decisions are sequential and observable copyright 1992 by american economic association

learning in a misspecified multivariate self referential linear stochastic model this paper introduces a general method to study stability under learning of equilibria resulting from agents with misspeci ed perceptions of the law of motion of the economy this is done by transforming the actual and perceived laws of motion into the form of seemingly unrelated regressions and then linearly projecting the actual law of motion into the same class as the perceived law of motion i study the new keynesian is lm model with inertia under all possible classes of restricted perceptions it turns out that the results found in bullard and mitra 2002 2003 are robust under misspeci ed expectations

heterogeneous expectations optimal monetary policy and the merit of policy inertia the design and analysis of optimal monetary policy is usually guided by the paradigm of homogeneous rational expectations instead we examine the dynamic consequences of design and implementation strategies when the actual economy features expectational heterogeneity agents have either rational or adaptive expectations consequently the central bank s ability to achieve price stability under heterogeneous expectations depends on its objective and implementation strategy an expectations based reaction function which appropriately conditions on private sector expectations performs exceptionally well however once the objective introduces policy inertia popular strategies have similar determinacy properties but they are less operational this finding calls for new implementation strategies under interest rate stabilization

trend inflation sticky prices and expectational stability abstract micro evidence indicates that each period a fraction of prices is kept unchanged under a positive trend inflation rate in a sticky price model based on this evidence recent research shows that high trend inflation is a serious cause for indeterminacy of rational expectations equilibrium under the taylor rule this paper examines implications of trend inflation for expectational stability of the equilibrium an empirically plausible calibration of the model demonstrates that a fundamental rational expectations equilibrium is likely to be expectationally stable even in cases of indeterminacy induced by high trend inflation

a new keynesian model with heterogeneous expectations abstract within a new keynesian model we incorporate bounded rationality at the individual agent level and we determine restrictions on expectations operators sufficient to imply aggregate is and as relations of the same functional form as those under rationality this result provides dual implications the strong nature of the restrictions required to achieve aggregation serve as a caution to researchers imposing heterogeneous expectations at an aggregate level may be ill advised on the other hand accepting the necessary restrictions provides for tractable analysis of expectations heterogeneity as an example we consider a case where a fraction of agents are rational and the remainder are adaptive and find specifications that are determinate under rationality may possess multiple equilibria in case of expectations heterogeneity

repeated real options optimal investment behaviour and a good rule of thumb abstract this paper extends the standard investment under uncertainty set up with a single investment option to the case of infinitely repeated options analytical solutions are derived and it is shown that repeated options not only imply a smaller value of waiting than in the case of a single option but also that the optimal stopping rule is affected differently by changes in underlying parameters this is shown to allow for the use of a simple hurdle rate rule as a good and robust approximation to optimal behaviour when investment options are repeated something which is unlikely in the single option case

a new keynesian model with staggered price and wage setting under learning abstract this paper provides a study of the implications for economic dynamics when the central bank sets its nominal interest rate target in response to variations in wage inflation i provide results on the existence uniqueness and stability under learning of rational expectations equilibrium for alternative specifications of the manner in which monetary policy responds to economic shocks when nominal rigidities are present monopolistically competitive producers set prices via staggered price contracts and households set nominal wages in the same fashion in this setting the conditions for determinacy and learnability of rational expectations equilibrium differ from a model where only prices are sticky i find that when the central bank responds to wage and price inflation and to the output gap a taylor principle for wage and price inflation arises that is related to stability under learning dynamics in other words a moderate reaction of the interest rate to wage inflation helps to avoid instability under learning and indeterminacy

on the fragility of sunspot equilibria under learning and evolutionary dynamics abstract in this article we investigate the possibility of sunspot equilibria to emerge from a process of learning and adaptation on agents beliefs we consider both finite state markov sunspots and sunspots in autoregressive form and derive conditions for the existence of an heterogeneous equilibrium where only a fraction of agents condition their forecasts on the sunspot we then show that when the fraction of agents conditioning their forecasts on a sunspot changes over time under evolutionary dynamics these restrictions need to evolve endogenously with population shares we argue that such requirement questions the possibility of sunspot equilibria to emerge through a process of evolution and adaptation on agents beliefs in order for a sunspot equilibrium to emerge all agents must simultaneously coordinate on the same sunspot variable at the same time

monetary policy and stable indeterminacy with inertia abstract we examine existence and stability under learning of sunspot equilibria in a new keynesian model incorporating inertia indeterminacy remains prevalent stable sunspots abound and inertia in is and aggregate supply as relations do not significantly impact the policy region containing stable sunspots

learning about monetary policy rules when the housing market matters abstract in this paper we study a general equilibrium model with a housing market and use stability under adaptive learning as a criterion to evaluate monetary policy rules an important feature of the model is that there exist credit constrained borrowers who use their housing assets as collateral to finance purchases we evaluate both conventional taylor rules and rules that incorporate other targets such as housing prices we find that the effect of responding to housing prices in addition to output and inflation depends critically on the assumed information structure of the economy

monetary policy indeterminacy and learning abstract forward looking monetary models with taylor type interest rate rules are known to generate indeterminacies with a potential dependence on extraneous sunspots for some structural and policy parameters we investigate the stability of these solutions under adaptive learning focusing on common factor or resonance frequency representations in which the observed sunspot has a suitable time series structure we consider specifications incorporating both lagged and expected inflation in the phillips curve and both expected and inertial elements in the policy rule we find that some policy rules can indeed lead to learnable sunspot solutions and we investigate the conditions under which this phenomenon arises

financial factors and monetary policy determinacy and learnability of equilibrium abstract we contribute to the debate on whether central banks should respond to financial factors in monetary policy rules by evaluating equilibrium determinacy and e stability in the presence of a financial accelerator policies responding to lagged asset prices either reduce the region of determinacy or e stability in the parameter space however a response to current asset prices expands both regions of determinacy and e stability policy rules reacting to credit volume constrict the determinacy region most policies responding to credit spreads expand determinacy and e stability regions we favor the inclusion of current asset prices or credit spreads in monetary policy rules

interest rate control and nonconvergence to rational expectations this paper investigates the feasibility of a monetary policy aimed at pegging the nominal rate of interest it shows that under general conditions such a policy would produce the well known cumulative process despite the fact that there exists a well behaved rational expectations equilibrium with no tendency for inflation to accelerate or decelerate the cumulative process shows up as the failure of learning to converge to rational expectations specifically the paper shows first in a conventional is lm model with an expectations augmented phillips curve and then in a micro based finance constraint model that if people follow any learning rule based on experience that satisfies a weak condition then the sequence of temporary equilibria under a policy of interest pegging cannot converge the nonconvergent path that will be observed accords with the familiar cumulative process in that inflation accelerates if the market rate of interest has been pegged below the natural rate

optimal fiscal policy under learning abstract this paper characterizes optimal fiscal policy when agents learn about future taxation a benevolent and fully rational government chooses taxes on labor income and state contingent bonds to finance public spending considering that private agents form their expectations through a learning algorithm facing a trade off between distortionary taxes and distorted expectations the ramsey planner chooses the policy that minimizes the total cost of distortions the analysis produces two main results first the government will use fiscal variables to manipulate expectations reducing taxes and issuing debt at times of pessimism and doing the opposite at times of optimism this speeds up learning second the expectation dependent fiscal plan is also history dependent and it prescribes taxes that are not as smooth and more persistent than under rational expectations these findings are robust to alternative learning algorithms

real time rational expectations and indeterminacy abstract this paper uses the technique of lubik and schorfheide lubik t schorfheide f 2004 testing for indeterminacy an application to u s monetary policy the american economic review 94 1 190 217 to test for indeterminacy in a new keynesian model using real time instead of revised data on the output gap the results suggest indeterminacy both before 1979 and after 1982

term structure evidence on interest rate smoothing and monetary policy inertia abstract numerous studies have used quarterly data to estimate monetary policy rules or reaction functions that appear to exhibit a very slow partial adjustment of the policy interest rate the conventional wisdom asserts that this gradual adjustment reflects a policy inertia or interest rate smoothing behavior by central banks however such quarterly monetary policy inertia would imply a large amount of forecastable variation in interest rates at horizons of more than 3 months which is contradicted by evidence from the term structure of interest rates the illusion of monetary policy inertia evident in the estimated policy rules likely reflects the persistent shocks that central banks face

social learning and monetary policy rules we analyse the effects of social learning in a monetary policy context social learning might be viewed as more descriptive of actual learning behaviour in complex market economies in our model taylor principle governs uniqueness and expectational stability of rational expectations equilibrium ree under homogeneous recursive algorithms we find that the taylor principle is not necessary for convergence to ree minimum state variable msv equilibrium under social learning sunspot equilibria exist in the indeterminate region our agents cannot co ordinate on a sunspot equilibrium in general form specification however they can co ordinate on common factor specification we contribute to the use of genetic algorithm learning in stochastic environments

optimal timing of technology adoption abstract in a dynamic programming framework this paper investigates the optimal timing of technology adoption by a competitive firm when technology choice is irreversible and the firm faces a stochastic innovation process with uncertainties about both the speed of the arrival and the degree of improvement of new technologies a numerical example illustrates how the optimal timing decision is affected by changes in parameter values reflecting market conditions the firm s initial technological attributes and the characteristics of the stochastic innovation process some of these effects turn out to be in sharp contrast to common intuition contrasting the optimal decision rule derived here with the rule obtained under the net present value shows that the former implies a slower pace of adoption than implied by the latter the optimal decision rule is generalized for the case of multiple technology switches and it is shown that for all the switching decisions except the last one the optimal rule satisfies the net present value criterion

investment under uncertainty the case of replacement investment decisions we analyze the determinants of replacement investment decisions in a contingent claims model with maintenance and operation cost uncertainty we find that the optimal time between replacements is increasing in the volatility of cost the purchase price of a new asset and the corporate tax rate and is decreasing in the systematic risk of cost the salvage value of the asset and the investment tax credit the optimal time between replacements can either increase or decrease with an increase in the depreciation rate extensions of the model to examine the effects of technological and tax policy uncertainty on replacement investment decisions give intuitive but striking results uncertainty about the arrival of a technological innovation that would decrease maintenance and operation cost results in a significant decrease in replacement investment uncertainty in a tax law change that would encourage investment decreases current investment and uncertainty in a tax law change that would discourage investment increases current investment

machine replacement under evolving deterministic and stochastic costs the infinite horizon cost minimization and the real option stopping problem are used to analyze serial replacement of a single asset under improving technology it is shown that both techniques produce the same equal life replacement policy when exponential technological improvements affect the operating cost and new asset cost in the same way next this result is extended to the stopping problem under evolving stochastic costs under general improving technology the expected asset lifetimes appear to be different for sequential replacement cycles and depend on the future cost evolution numeric experiments are provided and managerial implications of the obtained outcomes are discussed

are non fundamental equilibria learnable in models of monetary policy abstract recent models of monetary policy can have indeterminacy of equilibria which is often viewed as a difficulty of these models we consider the significance of indeterminacy using the learning approach to expectations formation we employ expectational stability as a selection criterion for different equilibria and derive the expectational stability and instability conditions for forward looking multivariate models both without and with lags the results are applied to several monetary policies

real business cycles and the animal spirits hypothesis abstract we calibrate a quantitative equilibrium macroeconomic model with an aggregate technology that is subject to increasing returns and show that this model may display fluctuations at business cycle frequencies even when there are no shocks to the fundamentals of the economy these fluctuations are due to the self fulfilling beliefs of investors which we call animal spirits we compare the impulse response functions predicted by our model and by two other more standard models with a four variable vector autoregression on u s data our animal spirits economy is the most successful of the three at matching broad features of the dynamic responses in the data journal of economic literature classification numbers e00 e3 e32

strategic technology switching under risk aversion and uncertainty abstract firms devising green investment strategies within a deregulated environment must take into account not only economic and technological uncertainty but also strategic interactions due to competition also further complicating green investment decisions is the fact that firms are likely to exhibit risk aversion since alternative energy technologies entail risk that cannot be diversified therefore we develop a utility based real options framework for pre emptive and non pre emptive competition in order to analyse how economic and technological uncertainty interact with risk aversion to impact the adoption of an existing technology in the light of uncertainty over the arrival of an improved version we confirm that greater risk aversion delays investment and show that technological uncertainty accelerates the follower s entry delays the entry of the pre emptive leader and intriguingly does not affect the non pre emptive leader s investment decision also we show how the relative loss in the leader s value due to the follower s entry is affected by economic and technological uncertainty as well as risk aversion and how the risk of pre emption under increasing economic uncertainty raises the value of direct investment in the new technology relative to stepwise investment