scientific ambiguity and climate policy economic evaluation of climate policy traditionally treats uncertainty by appealing to expected utility theory yet our knowledge of the impacts of climate policy may not be of sufficient quality to be described by unique probabilistic beliefs in such circumstances it has been argued that the axioms of expected utility theory may not be the correct standard of rationality by contrast several axiomatic frameworks have recently been proposed that account for ambiguous knowledge in this paper we apply static and dynamic versions of a smooth ambiguity model to climate mitigation policy we obtain a general result on the comparative statics of optimal abatement and ambiguity aversion and then extend our analysis to a more realistic dynamic setting where we introduce scientific ambiguity into the well known dice model of the climate economy system for policy relevant exogenous mitigation policies we show that the value of emissions abatement increases as ambiguity aversion increases and that this ambiguity premium can in some plausible cases be very large in these cases the effect of ambiguity aversion on welfare is comparable to that of other much studied welfare parameters thus ambiguity aversion may be an important neglected aspect of climate change economics and seems likely to provide another argument for strong abatement policy

ambiguity aversion and the preference for established brands we propose that ambiguity aversion as introduced in the literature on decision making under uncertainty drives a preference for established brands in multiattribute choices among branded alternatives established brands are those for which belief in quality is held with greater confidence even if specific attributes might be inferior to those of competing less established brands in five experiments we examine the role of ambiguity aversion in the preference for dominated established brands we first show a correlation between ambiguity aversion revealed through choices among monetary lotteries and the preference for established brands we then show that the preference for established brands is enhanced when ambiguity aversion is made more salient in unrelated preceding lottery choices thus ambiguity aversion carries across choices in addition ambiguity aversion and the preference for established brands are both enhanced when subjects anticipate that others will evaluate their lottery choices finally ambiguous information about brand attributes tends to increase the preference for established brands

time inconsistent preferences and social security in this paper we examine the role of social security in an economy populated by overlapping generations of individuals with time inconsistent preferences who face mortality risk individual income risk and borrowing constraints we find that unfunded social security lowers the capital stock output and consumption for consumers with time consistent or time inconsistent preferences however it may raise or lower welfare depending on the strength of time inconsistency

reduction of compound lotteries with objective probabilities theory and evidence abstract the reduction of compound lotteries axiom rocl has assumed a central role in the evaluation of behavior toward risk and uncertainty we present experimental evidence on its validity in the domain of objective probabilities our battery of lottery pairs includes simple one stage lotteries two stages compound lotteries and their actuarially equivalent one stage lotteries we find violations of rocl and that behavior is better characterized by a source dependent version of the rank dependent utility model rather than expected utility theory since we use the popular 1 in k random lottery incentive mechanism payment procedure in our main test our experiment explicitly recognizes the impact that this payment procedure may have on preferences thus we also collect data using the 1 in 1 payment procedure we do not infer any violations of rocl when subjects are only given one decision to make these results are supported by both structural estimation of latent preferences as well as non parametric analysis of choice patterns the random lottery incentive mechanism used as payment protocol itself induces an additional layer of compounding by design that might create confounds in tests of rocl therefore we provide a word of caution for experimenters interested in studying rocl for other purposes such as the relationship between ambiguity attitudes and attitudes toward compound lotteries to carefully think about the design to study rocl payment protocols and their interaction with the preferences being elicited

macroeconomics after the crisis time to deal with the pretense of knowledge syndrome the recent financial crisis has damaged the reputation of macroeconomics largely for its inability to predict the impending financial and economic crisis to be honest this inability to predict does not concern me much it is almost tautological that severe crises are essentially unpredictable for otherwise they would not cause such a high degree of distress what does concern me about my discipline is that its current core by which i mainly mean the so called dynamic stochastic general equilibrium approach has become so mesmerized with its own internal logic that it has begun to confuse the precision it has achieved about its own world with the precision that it has about the real one this is dangerous for both methodological and policy reasons to be fair to our field an enormous amount of work at the intersection of macroeconomics and corporate finance has been chasing many of the issues that played a central role during the current crisis including liquidity evaporation collateral shortages bubbles crises panics fire sales risk shifting contagion and the like however much of this literature belongs to the periphery of macroeconomics rather than to its core i will discuss the distinction between the core and the periphery of macroeconomics as well as the futile nature of the integrationist movement that is the process of gradually bringing the insights of the periphery into the dynamic stochastic general equilibrium structure i argue that the complexity of macroeconomic interactions limits the knowledge we can ever attain and that we need to place this fact at the center of our analysis we should consider what this complexity does to the actions and reactions of the economic agent and seek analytical tools and macroeconomic policies that are robust to the enormous uncertainty to which we are confined

money and economic activity inventories and business cycles abstract incomplete information is a necessary condition for any real effects produced by monetary impulses an alternative to the local global inference problem is explored in this paper agents are confronted with permanent and transitory shocks even with full knowledge about the stochastic structure their best perception at any particular time will usually be erroneous prices for each period are set at the beginning of the period on the basis of market conditions the realization of the shock process thus creates a short run disequilibrium absorbed by inventory adjustments this adjustment translates perceived transitory monetary shocks into serially correlated output movements the analysis proceeds within the context of rational expectations it offers a generalization of equilibrium analysis in two respects prices are always in equilibrium relative to perceived conditions but they do not reflect all ongoing shocks quantity adjustments reflect the perceived transitory shocks the framework used involves moreover a stock flow interaction operated by inventory adjustments the stock flow interaction imposes at any time a future expected adjustment path for price level and quantities to the system s unique stock equilibrium a major implication of the analysis resolves a puzzle experienced in a recent paper by robert hall it reconciles intertemporal substitution with lagged effects of monetary impulses it also reconciles small and inconclusive cyclic movements in real wages with the occurrence of production function and large variations in unemployment lastly the nature of the inference problem determined by the pattern of incomplete information produces serially correlated movements conditioned on large permanent shocks

micro and macro elasticities in a life cycle model with taxes we build a life cycle model of labor supply that incorporates changes along both the intensive and extensive margin and use it to assess the consequences of changes in tax and transfer policies on equilibrium hours of work we find that changes in taxes have large aggregate effects on hours of work moreover we find that there is no inconsistency between this result and the empirical finding of small labor elasticities for prime age workers in our model micro and macro elasticities are effectively unrelated our model is also consistent with other cross country patterns

actively learning about demand and the dynamics of price adjustment by observing the quantity demanded at particular prices a firm may learn about the parameters of its demand curve in such an environment price changes obstruct the learning process by inducing additional noise the authors paper constructs a dynamic model where a price setting firm endogenously controls the speed of learning the model provides a possible explanation for price inertia as a stable pricing policy allows the firm to learn more rapidly which improves future expected profits furthermore even in the long run learning continues to affect the firm s optimal price copyright 1990 by royal economic society

knight on risk and uncertainty it is argued that the received interpretation of knight s classic riskuncertainty distinction as concerning whether or not agents have subjective probabilities constitutes a misreading of knight on the contrary knight shared the modern view that agents can be assumed always to act as if they have subjective probabilities we document our contention that by uncertainty knight instead meant situations in which insurance markets collapse because of moral hazard or adverse selection knight s discussion of market failure although always informal and in places inaccurate was in many respects a remarkable anticipation of the modern literature

real wages over the business cycle evidence from panel data one topic on which keynes did not disagree with classical economists was the cyclical behavior of real wages keynes 1936 as well as various classical writers predicted that real wages should move countercyclically quoting the general theory p 17 in general an increase in employment can only occur through the accompaniment of a decline in real wages thus i am not disputing this vital fact which the classical economists have rightly asserted as indefeasible this prediction is based on the premise of competition and a given short run capital stock increases in employment then correspond to more intensive use of capital and through diminishing product lower real wages for this reason evidence by dunlop 1938 and tarshis 1939 that real wages move procyclically was viewed as paradoxical both dunlop and tarshis based their findings on an observed positive correlation between real and money wages which given the procyclical movement of money wages implies a positive correlation between

quasi hyperbolic discounting and retirement abstract some people have self control problems regularly this paper adds endogenous retirement to laibson s quasi hyperbolic discounting savings model quarterly journal of economics 112 1997 443 477 earlier selves think that the deciding self tends to retire too early and may save less to induce later retirement still earlier selves may think the pre retirement self does this too much saving more to induce early retirement the consumption pattern may be different from that with exponential discounting other observational non equivalence includes the impact of changing mandatory retirement rules or work incentives on savings and a possibly negative marginal propensity to consume out of increased future earnings naive agents are briefly considered

dynamic consistency and regret abstract individuals often report that they regret not having saved more for retirement this fact raises concerns about the financial security of retirees and about the adequacy of traditional economic models in making predictions that are consistent with regret about having saved too little for retirement we provide an overview of four discounted utility models and examine their implications for the optimal level of retirement savings all of these models exhibit dynamically consistent decision making and some also feature backward discounting in order to generate regret about past saving decisions in our preferred parameterization with both forward and backward discounting a 66 year old at retirement will consider the optimal level of retirement savings to be almost twice as large as what was actually saved even though actual saving decisions are dynamically consistent across the entire life cycle compared to a model setting with fixed retirement adding choice over retirement timing compounds the regret that individuals experience about past saving decisions

adjustment to production uncertainty and the theory of the firm a comment this paper reconsiders the model presented by flacco and kroetch 1986 it shows that with additive technological uncertainty the firm will produce and contract to sell the same output as under certainty when the flacco kroetch model is generalized to allow the firm to select contract commitments and planned output ex ante no simple comparisons with certainty are possible these results are broadly consistent with those obtained by mills 1959 1962 for demand uncertainty

providing global public goods under uncertainty abstract we study how uncertainty and risk aversion affect international agreements to supply global public goods we consider a benchmark model with homogeneous countries and linear payoffs when countries directly contribute to a public good uncertainty tends to lower signatories efforts but may increase participation despite risk aversion uncertainty may improve welfare in contrast when countries try to reduce a global public bad uncertainty tends to increase signatories efforts and decrease participation in that case an ex ante reduction of uncertainty may have a large positive multiplier effect on welfare

addiction and cue triggered decision processes we propose a model of addiction based on three premises 1 use among addicts is frequently a mistake 2 experience sensitizes an individual to environmental cues that trigger mistaken usage 3 addicts understand and manage their susceptibilities we argue that these premises find support in evidence from psychology neuroscience and clinical practice the model is tractable and generates a plausible mapping between behavior and the characteristics of the user substance and environment it accounts for a number of important patterns associated with addiction gives rise to a clear welfare standard and has novel implications for policy

the output inflation relationship abstract this paper shows how the optimal pricing and production policy of a multiperiod profit maximizing firm under demand and output disturbances leads in the aggregate to a positive relationship between production and price deviations from the expected level as depicted by the lucas type supply function the pricing and production decisions are made simultaneously by market agents who base their decisions on the same rational expectations before the disturbances are realized here although the planned production is not affected by the price deviations there is still a contemporaneous positive relationship between them where both production and prices reflect the firm s adjustment to unexpected levels of inventory we show that this positive relationship prevails even when the production decisions are made ex ante based only on expectations before the realization of the random shocks a closed form linear approximation for the supply function is derived which captures the effect of both systematic and unsystematic economic disturbances finally we present an empirical test which supports our assertion that our inventory adjustment mechanism contributes to the creation of the positive relationship between production and price deviations

measuring self control problems we develop a survey instrument to measure self control problems in a sample of highly educated adults this measure relates in the manner that theory predicts to liquid wealth accumulation and personality measures yet while self control problems are typically seen as resulting in overconsumption and low wealth we identify a significant group who underconsume and thereby accumulate high levels of wealth in addition self control problems are smaller in scale for older than for younger respondents those who put money aside in retirement accounts may be delaying access to a point at which self control problems are no longer important jel d12 d14

lifetime consumption and investment retirement and constrained borrowing retirement flexibility and inability to borrow against future labor income can significantly affect optimal consumption and investment with voluntary retirement there exists an optimal wealth to wage ratio threshold for retirement and human capital correlates negatively with the stock market even when wages have zero or slightly positive market risk exposure consequently investors optimally invest more in the stock market than without retirement flexibility both consumption and portfolio choice jump at the endogenous retirement date the inability to borrow limits hedging and reduces the value of labor income the wealth to wage ratio threshold for retirement and the stock investment

the social discount rate what discount rate should be applied to social investments it is standard to use the market interest rate thereby respecting private preferences we show that application of this revealed preference criterion rests on faith not on logic it is justified only if preferences over all choices including past choices are time invariant the conditions for this to be true are stringent under more reasonable conditions policy makers should be more patient than private citizens whose choices define the most short sighted pareto optimum

are policymakers ambiguity averse we investigate the ambiguity preferences of a unique sample of real life policymakers at the paris un climate conference cop21 we find that policymakers are generally ambiguity averse using a simple design we are moreover able to show that these preferences are not necessarily due to an irrational behaviour but rather to intrinsic preferences over unknown probabilities exploring the heterogeneity within our sample we also show that the country of origin and the degree of quantitative sophistication affect policymakers attitudes towards compound risk but not towards ambiguity robustness results are obtained in a lab experiment with a sample of university students

managing catastrophic climate risks under model uncertainty aversion we propose a robust risk management approach to deal with the problem of catastrophic climate change that incorporates both risk and model uncertainty using an analytical model of abatement we show how aversion to model uncertainty influences the optimal level of mitigation we disentangle the role of preferences from the structure of model uncertainty which we define by means of a simple measure of disagreement across models with data from an expert elicitation about climate change catastrophes we quantify the relative importance of these two effects and calibrate a numerical integrated assessment model of climate change the results indicate that the structure of model uncertainty and specifically how model disagreement varies in abatement is the key driver of optimal abatement and that model uncertainty warrants a higher level of climate change mitigation this paper was accepted by manel baucells decision analysis

money supply variability in a macro model of monopolistic competition the effects of changes in money supply variability are examined for a macro model of monopolistic competition increases in money supply variability raise demand uncertainty causing individual firms to produce more for inventory in addition expected profits decrease inducing a number of firms to leave the economy aggregate income then falls in spite of an increase in firm level production the result on aggregate income is standard but the results on inventories and the number of firms in the economy distinguish this monopolistic macro model empirically from conventional macro models when changes in money supply variability occur

are people risk vulnerable we report on a within subject experiment with substantial monetary incentives designed to test whether or not people are risk vulnerable in the experiment subjects face the standard portfolio choice problem in which the investor has to allocate part of his wealth between one safe asset and one risky asset we elicit risk vulnerability by observing each subject s portfolio choice in two different contexts that differ only by the presence or absence of an actuarially neutral background risk our main result is that most of the subjects are risk vulnerable 81 chose a less risky portfolio when exposed to background risk more precisely 47 invested a strictly smaller amount in the risky asset whereas 34 were indifferent furthermore contrasting the predictions provided by competing decision theoretic models we conclude that expected utility theory best fits our experimental data this paper was accepted by uri gneezy behavioral economics

model uncertainty in climate change economics a review and proposed framework for future research we review recent models of choices under uncertainty that have been proposed in the economic literature in particular we show how different concepts and methods of economic decision theory can be directly useful for problems in environmental economics the framework we propose is general and can be applied in many different fields of environmental economics to illustrate we provide a simple application in the context of an optimal mitigation policy under climate change

factor demand under conditions of product demand and supply uncertainty the paper develops a theory of factor demand under uncertainty that encompasses neo classical factor demand and keynesian effective factor demand as special cases the model allows factor demand and output to move positively with product demand even with a constant product price this in turn permits real wages to move pro cyclically in response to product demand shocks in addition the model provides a new perspective on the adding up problem which posits that total factor payments exceed output if increasing returns to scale exist and generates positive uncertainty profits that are similar in spirit to those of frank knight

climate contracts a game of emissions investments negotiations and renegotiations the paper presents a dynamic game where players can contribute to a public bad invest in technologies and write incomplete contracts despite the n 1 stocks in the model the analysis is tractable and the symmetric markov perfect equilibrium unique the framework helps to analyze emissions investments and international environmental agreements if only the emission levels are contractible then investments are suboptimally small if the contract is short term or close to its expiration date to encourage investments the optimal contract is more ambitious if it is short term and it is tougher to satisfy close to its expiration date and for countries with small investment costs if renegotiation is possible such an incomplete contract implements the rst best the results have important lessons for how to design a climate treaty

toward a theory of rigidities this paper presents a theory of rigidity or more properly inertia in the responses of economic variables to changing environments the theory rests on three fundamental assumptions 1 that firms are risk averse 2 that firms are uncertain of the impacts of changing decision variables and 3 that this uncertainty increases with the size of deviations in decision variables from appropriately defined past level under these circumstances an optimal portfolio of incremental decision variable adjustments exists which a takes variance minimizing adoptions to environmental change as a point of departure and then b is weighted in favor of changes in variables whose effects are less uncertain in considering price and quantity adjustments this implies that price and wage adjustments should largely incorporate expected inflation and from that point should be small relative to quantity adjustments since in most situations the uncertainties associated with the consequences of quantity adjustment should be smaller than those associated with price adjustments this abstract was borrowed from another version of this item

retirement pensions and ageing we study the effects of demographic shocks and changes in the pension system on the macroeconomic performance of an advanced small open economy facing a given world interest rate we construct an overlapping generations model which includes a realistic description of the mortality process individual agents choose their optimal retirement age taking into account the time and age profiles of wages taxes and the public pension system the early retirement provision in most pension systems acts as a trap inducing most workers to retire well before the normal retirement age simulations show that pension reform must be drastic for it to have any effects on the retirement behaviour of workers

the rich domain of uncertainty source functions and their experimental implementation we often deal with uncertain events for which no probabilities are known several normative models have been proposed descriptive studies have usually been qualitative or they estimated ambiguity aversion through one single number this paper introduces the source method a tractable method for quantitatively analyzing uncertainty empirically the theoretical key is the distinction between different sources of uncertainty within which subjective choice based probabilities can still be defined source functions convert those subjective probabilities into willingness to bet we apply our method in an experiment where we do not commit to particular ambiguity attitudes but let the data speak

selfcon rming equilibrium and model uncertainty we propose to bring together two conceptually complementary ideas 1 selfcon rming equilibrium sce at rest points of learning dynamics in a game played recurrently agents best respond to con rmed beliefs i e beliefs consistent with the evidence they accumulated and 2 ambiguity aversion agents other things being equal prefer to bet on events with known rather than unknown probabilities and more generally distinguish objective from subjective uncertainty a behavioral trait captured by their ambiguity attitudes using as a workhorse the smooth ambiguity model of klibano marinacci and mukerji 2005 we provide a de nition of smooth sce which generalizes the traditional concept of fudenberg and levine 1993a b here called bayesian sce and admits waldean maxmin sce as a limit case we show that the set of equilibria expands as ambiguity aversion increases the intuition is simple by playing the same strategy in

competitive firm behavior under risk in disequilibrium trading the objective of this paper is to study the behavior of the purely competitive firm in a market in which traders plans may not be realized each period the emphasis of the study is motivated by a desire to introduce explicit price makers into the theory of competitive markets the method of introducing price makers may lead to situations in which markets are not cleared each period and shortages may arise with the realization of plans being in doubt in this environment traders learn to adjust decisions to offset periodic disappointment multiperiod models are introduced to analyze the decision process of the competitive firm in the market and stochastic dynamic programming methods are used to obtain characteristics of optimal plans results are compared to the situation in which plans are always realized

can uncertainty alleviate the commons problem global commons problems such as climate change are often affected by severe uncertainty the paper examines the effect of uncertainty on pollution emissions and welfare in a strategic context we find that emissions are always lower under uncertainty than under certainty reflecting risk reducing considerations we show that uncertainty can have a net positive impact on the welfare of risk averse polluters we extend the analysis to increases in risk increases in risk aversion and to risk heterogeneity jel d81 c72 q54 h23

decreasing impatience a criterion for non stationary time preference and hyperbolic discounting despite recent interest in hyperbolic discounting there has been little discussion of exactly what property of time preferences is instantiated by hyperbolic or quasi hyperbolic functional forms the paper revives an earlier proposal in prelec 1989 that the key property is prattarrow convexity of the log of the discount function which corresponds to decreasing impatience di at the level of preferences di provides a natural criterion for assessing the severity of departure from stationarity in that greater di is equivalent to more choices of dominated options in two stage decision problems as well as greater convexity of the log of the discount function inefficient choices may arise as intentional precommitments or as unintended reversals of preference by naive agents

ambiguity aversion and household portfolio choice puzzles empirical evidence we test the relation between ambiguity aversion and five household portfolio choice puzzles nonparticipation in equities low allocations to equity home bias own company stock ownership and portfolio under diversification in a representative us household survey we measure ambiguity preferences using custom designed questions based on ellsberg urns as theory predicts ambiguity aversion is negatively associated with stock market participation the fraction of financial assets in stocks and foreign stock ownership but it is positively related to own company stock ownership conditional on stock ownership ambiguity aversion is related to portfolio under diversification and during the financial crisis ambiguity averse respondents were more likely to sell stocks

advantage to a risk neutral firm of flexible resources under demand uncertainty this paper shows that flexible resources resources that can be resold or switched between productive processes are valuable to firms facing uncertain demand it is assumed that the firm must make its input purchase decision before the demand for its final product is known it is this differential in timing of the purchase of inputs versus selling of outputs which is the special problem confronted in this paper and which makes the existence of a flexible resource valuable to the firm stigler in a 1939 article recognized that in a risky environment there are advantages to resources which are flexible but did not provide an optimizing model in his analysis 4 others such as turnovsky 5 appelbaum and lim 1 sheppard 3 and epstein 2 have examined this timing problem and have recognized as we do that in a market characterized by uncertainty a firm will face a trade off between efficiency and flexibility 1 39 however the issue of the advantage of flexible resources under uncertainty has not been directly examined usually because the focus has been on outputs rather than inputs 1 or on attitudes toward risk even when input choice is responsive to uncertainty as in epstein 2 the inputs are not flexible in our sense because it is only the timing of input purchase which is flexible not the uses to which inputs can be assigned of the several ways uncertainty in demand can be conceptualized for the firm these papers have commonly considered a situation where it is the product price which is uncertain 2 5 in contrast this paper assumes that while price is known the quantity demanded is uncertain this allows us to consider a slightly different kind of firm from the previous work the firm is assumed to be a pure price taker it might be in an oligopolistic industry where total industry demand is known but the market share for each firm has yet to be revealed 2 or the firm might be in a regulated industry where prices are set and all market adjustments come on the quantity side

ambiguity reasoned determination and climate change policy abstract this paper examines climate change benefit cost analysis in the presence of scientific uncertainty in the form of ambiguity the specific issue addressed is the robustness of benefit cost analyses of climate change policy alternatives to relaxation of savage s original axioms two alternatives to subjective expected utility seu are considered maximin expected utility meu and incomplete expected utility ieu among other results it is demonstrated that polar opposite recommendations can emerge in an ambiguous decision setting even if all agree on society s rate of time preference society s risk attitudes the degree of ambiguity faced and the scientific primitives we show that for a simple numerical simulation of our model an meu decision maker favors policies which immediately tackle climate change while an ieu decision prefers business as usual each agency shall assess the costs and benefits of the intended regulation and recognizing that some costs and benefits are difficult to quantify propose or adopt a regulation only upon a reasoned determination that the benefits of the intended regulation justify its cost executive order 12866 of the us president

ambiguity attitudes in a large representative sample using a theorem showing that matching probabilities of ambiguous events can capture ambiguity attitudes we introduce a tractable method for measuring ambiguity attitudes and apply it in a large representative sample in addition to ambiguity aversion we confirm an ambiguity component recently found in laboratory studies a insensitivity the tendency to treat subjective likelihoods as 50 50 thus overweighting extreme events our ambiguity measurements are associated with real economic decisions specifically a insensitivity is negatively related to stock market participation ambiguity aversion is also negatively related to stock market participation but only for subjects who perceive stock returns as highly ambiguous this paper was accepted by james smith decision analysis

a note on adjustment to production uncertainty and the theory of the firm this paper analyzes the impact of production uncertainty on the firm s optimal output decision if uncertainty is introduced by an additive risk variable then short run optimal output is unchanged but the owner manager s expected utility can change causing long run output effects if uncertainty is introduced by a multiplicative random variable then short run output can change as well

real business cycles in this paper we demonstrate how certain very ordinary economic principles lead maximizing individuals to choose consumption production plans that display many of the characteristics commonly associated with business cycles our explanation is entirely consistent with i rational expectations ii complete current information iii stable preferences iv no technological change v no long lived commodities vi no frictions or adjustment costs vii no government viii no money and ix no serial dependence in the stochastic elements of the environment we also provide a completely worked out example of the type of artificial economy we have in mind the time series properties of the example exhibit some major features of observed business cycles although this type of model may not be capable of explaining all of the regularities in actual business cycles we believe that it provides a useful well defined benchmark for assessing the relative importance of factors e g monetary disturbances