intrinsic bubbles the case of stock prices several puzzling aspects of the behavior of united states stock prices may be explained by the presence of a specific type of rational bubble that depends exclusively on aggregate dividends the authors call bubbles of this type intrinsic bubbles because they derive all of their variability from exogenous economic fundamentals and none from extraneous factors intrinsic bubbles provide a more plausible empirical account of deviations from present value pricing than do the traditional examples of rational bubbles their explanatory potential comes partly from their ability to generate persistent deviations that appear to be relatively stable over long periods copyright 1991 by american economic association

optimal policy in markov switching rational expectations models abstract in this paper we consider the optimal quadratic control problem of markov switching linear rational expectation models these models are general and flexible tools for modelling not only regime but also model or parameter uncertainty we show first how to find the solution of a markov switching linear rational expectation model based on this solution we then show how to apply dynamic programming to find the optimal time consistent policy and the resulting nash stackelberg equilibrium suitable modifications of the algorithm allow to deal with the non re case in which the policymaker and the private sector hold different beliefs or probabilities over regime change we also show how the optimisation procedure can be employed to obtain the optimal policy under commitment as an illustration we compute the optimal policy in a small open economy subject to stochastic structural breaks in some of its key parameters

inflation price level and hybrid rules under inflation uncertainty the performance and robustness of optimised interest rate rules are analysed in a new keynesian model estimated for the euro area economy in particular we examine the properties of rules responding to inflation the price level or a combination of the two a hybrid rule all the rules also respond to the output gap the optimal hybrid rule is only marginally superior when there is no model uncertainty when there is uncertainty about the degree of inflation persistence the inflation rule is the most robust rule and the performance of the other two rules deteriorates however all the rules perform well if the true degree of inflation persistence turns out to be less than policymakers estimate

slow boom sudden crash abstract many asset markets exhibit slow booms and sudden crashes this pattern is explained by an endogenous flow of information in the model agents undertake more economic activity in good times than in bad economic activity generates public information about the state of the economy if the economic state changes when times are good and information is abundant asset prices adjust quickly and a sudden crash occurs when times are bad scarce information and high uncertainty slow agents reactions as the economy improves a gradual boom ensues data from u s and emerging credit markets support the theory

u s monetary regimes and optimal monetary policy in the euro area monetary policy in the united states has been documented to have switched from reacting weakly to inflation fluctuations during the 1970s to fighting inflation aggressively from the early 1980s onward in this paper i analyze the impact of the u s monetary policy regime switches on the eurozone i construct a new keynesian two country model where foreign u s monetary policy switches regimes over time i estimate the model for the u s and the euro area using quarterly data and find that the united states has switched between those two regimes in line with existing evidence i show that foreign regime switches affect home eurozone inflation and output volatility and their responses to shocks substantially as long as the home central bank commits to a time invariant interest rate rule reacting to domestic conditions only optimal policy in the home country instead requires that the home central bank reacts strongly to domestic producer price inflation and to international variables such as imported goods relative prices in fact i show that currency misalignments and relative prices play a crucial role in the transmission of foreign monetary policy regime switches internationally interestingly i show that only marginal gains arise for the euro area when the european central bank ecb adjusts its policy according to the monetary regime in the united states thus a simple time invariant monetary policy rule with a strong reaction to producer price index ppi inflation and relative prices is enough to counteract the effects of monetary policy switches in the united states

the new uk monetary arrangements a view from the literature this paper considers the likely operating characteristics of the new uk monetary arrangements introduced in may 1997 the paper first argues that the time inconsistency of policy is not an issue provided the bank of england is properly independent however the current inflation remit from the chancellor to the bank specifies a numerical target for the inflation rate but does not specify how quickly deviations from the target are to be corrected it is thus an incomplete contract and there is a danger that the bank may choose to stabilise inflation at the cost of excessively volatile movements in output or vice versa we estimate the optimal policy frontier for the uk economy and show that in practice it is close to rectangular consequently all the bank needs to assume is that the government s preferences are reasonable in order to know approximately where to locate on this frontier the incompleteness of the remit therefore need not be a cause for concern

robust monetary policy with competing reference models abstract the existing literature on robust monetary policy rules has largely focused on the case in which the policymaker has a single reference model while the true economy lies within a specified neighborhood of the reference model in this paper we show that such rules may perform very poorly in the more general case in which non nested models represent competing perspectives about controversial issues such as expectations formation and inflation persistence using bayesian and minimax strategies we then consider whether any simple rule can provide robust performance across such divergent representations of the economy we find that a robust outcome is attainable only in cases where the objective function places substantial weight on stabilizing both output and inflation in contrast we are unable to find a robust policy rule when the sole policy objective is to stabilize inflation we analyze these results using a new diagnostic approach namely by quantifying the fault tolerance of each model economy with respect to deviations from optimal policy

monetary policy regimes and beliefs this paper investigates the role of beliefs over monetary policy in propagating the effects of monetary policy shocks within the context of a dynamic stochastic general equilibrium model in this model monetary policy periodically switches between low and high money growth regimes when individuals cannot observe the regime directly they must draw inferences over regime type based on historical money growth rates the authors show that for an empirically plausible money growth process beliefs evolve slowly in the wake of a regime change as a result their model is able to capture some of the observed persistence of real and nominal variables following such a regime change

should central banks respond to movements in asset prices in recent decades asset booms and busts have been important factors in macroeconomic fluctuations in both industrial and developing countries in light of this experience how if at all should central bankers respond to asset price volatility we have addressed this issue in previous work bernanke and gertler 1999 the context of our earlier study was the relatively new but increasingly popular monetary policy framework known as inflation targeting see e g bernanke and frederic mishkin 1997 in an inflation targeting framework publicly announced medium term inflation targets provide a nominal anchor for monetary policy while allowing the central bank some flexibility to help stabilize the real economy in the short run the inflation targeting approach gives a specific answer to the question of how central bankers should respond to asset prices changes in asset prices should affect monetary policy only to the extent that they affect the central bank s forecast of inflation to a first approximation once the predictive content of asset prices for inflation has been accounted for there should be no additional response of monetary policy to assetprice fluctuations in use now for about a decade inflationtargeting has generally performed well in practice however so far this approach has not often been stress tested by large swings in asset prices our earlier research employed simulations of a small calibrated macroeconomic model to examine how an inflation targeting policy defined as one in which the central bank s instrument interest rate responds primarily to changes in expected inflation might fare in the face of a boom and bust cycle in asset prices we found that an aggressive inflationtargeting policy rule in our simulations one in which the coefficient relating the instrument interest rate to expected inflation is 2 0 substantially stabilizes both output and inflation in scenarios in which a bubble in stock prices develops and then collapses as well as in scenarios in which technology shocks drive stock prices intuitively inflation targeting central banks automatically accommodate productivity gains that lift stock prices while offsetting purely speculative increases or decreases in stock values whose primary effects are through aggregate demand conditional on a strong policy response to expected inflation we found little if any additional gains from allowing an independent response of central bank policy to the level of asset prices in our view there are good reasons outside of our formal model to worry about attempts by central banks to influence asset prices including the fact that as history has shown the effects of such attempts on market psychology are dangerously unpredictable hence we concluded that inflationtargeting central banks need not respond to asset prices except insofar as they affect the inflation forecast in the spirit of recent work on robust control the exercises in our earlier paper analyzed the performance of policy rules in worst case discussants robert shiller yale university glenn rudebusch federal reserve bank of san francisco kenneth rogoff harvard university

receding horizon control of jump linear systems and a macroeconomic policy problem abstract we study a time variant macroeconomic model in which some of the parameters are allowed to fluctuate in an exogenous form according to a markov chain this feature allows us to model abrupt changes for improvement and degradation in terms of the intrinsic relations of the economic variables and account for changes in the policy maker s preferences receding horizon control is well suited to systems with a modelled parameter fluctuation in the short and medium terms but with unmodelled uncertainties in the long run the problem features a partial information structure since the changes in the economy may not be accessible and to seek a computable solution we restrict attention to the class of linear feedback controls

optimal monetary policy in a regime switching economy the response to abrupt shifts in exchange rate dynamics abstract this paper examines the trade offs that a central bank faces when the exchange rate can experience sustained deviations from fundamentals and occasionally collapse the economy is modelled as switching randomly between different regimes according to time invariant transition probabilities we compute both the optimal regime switching control rule for this economy and optimised linear taylor rules in the two cases where the transition probabilities are known with certainty and where they are uncertain the simple algorithms used in the computation are also of independent interest as tools for the study of monetary policy under general forms of asymmetric additive and multiplicative uncertainty an interesting finding is that policies based on robust minmax values of the transition probabilities are usually more conservative

inflation zone targeting abstract we study optimal monetary policy design in a simple model that deviates from the linear quadratic paradigm and provides a rationale for the practice of inflation zone targeting we show that the presence of either zone quadratic preferences or a zone linear relationship between inflation and economic activity provides strong incentives to deviate from conventional linear policies we calibrate the model based on parameters for the united states and the euro area and employ a numerical dynamic programming algorithm to derive the optimal policies with this algorithm we examine the role of uncertainty model structure and relative preference towards economic stability in determining the width of the implied targeted inflation zone

durables and wives employment yet again the literature examining the relationship between consumer durables expenditures and wives employment is analyzed several deficiencies in the literature are corrected in a revised model that is estimated with data from the 1977 1978 survey of consumer expenditures this article concludes that durables expenditures and wives employment time are complements

consumption real exchange rates and the structure of international asset markets abstract international real business cycle irbc models that assume complete asset markets yield strong restrictions for consumption and bilateral real exchange rate series empirical tests with data for the us japan france uk italy canada and sweden suggest that neither the trend behavior nor high frequency movements of consumption and real exchange rates are well explained by irbc models with complete markets it appears however that high frequency fluctuations of consumption and real exchange rates are consistent with unrestricted international trade in risk free bonds

monetary regime switches and central bank preferences monetary policy objectives and targets are not necessarily constant over time the regime switching literature has typically analyzed and interpreted changes in policymakers behavior through simple interest rate rules this paper analyzes policy regime switches by explicitly modeling policymakers behavior and objectives we show that changes in the parameters of simple rules do not necessarily correspond to changes in policymakers preferences in fact capturing and interpreting regime changes in preferences through interest rate rules can lead to misleading results

monetary policy with uncertain parameters this thesis contains four chapters each of which examines different aspects of the uncertainty facing monetary policymakers monetary policy and market interest rates investigates how interest rates set on financial markets respond to policy actions taken by the monetary authorities the reaction of market rates is shown to depend crucially on market participants interpretation of the factors underlying the policy move these theoretical predictions find support in an empirical analysis of the u s financial markets predicting monetary policy using federal funds futures prices examines how prices of federal funds futures contracts can be used to predict policy moves by the federal reserve although the futures prices exhibit systematic variation across trading days and calendar months they are shown to be fairly successful in predicting the federal funds rate target that will prevailafter the next meeting of the federal open market committee from 1994 to 1998 monetary policy with uncertain parameters examines the effects of parameter uncertainty on the optimal monetary policy strategy under certain parameter configurations increasing uncertainty is shown to lead to more aggressive policy in contrast to the accepted wisdom should central banks be more aggressive examines why a certain class of monetary policy models leads to more aggressive policy prescriptions than what is observed in reality these counterfactual results are shown to be due to model restrictions rather than central banks being too cautious in their policy behavior an unrestricted model taking the dynamics of the economy and multiplicative parameter uncertainty into account leads to optimal policy prescriptions which are very close to observed federal reserve behavior

what is wrong with taylor rules using judgment in monetary policy through targeting rules it is argued that inflation targeting is best understood as a commitment to a targeting rule rather than an instrument rule e ither ageneral targeting rule explicit objectives for monetary policy or a specific targeting rule a criterion for the forecasts of the target variables to be fulfilled essentially the equality of the marginal rates of transformation and substitution between the target variables targeting rules allow the use of judgment and extramodel information are more robust and easier to verify than optimal instrument rules and they can nevertheless bring the economy close to the socially optimal equilibrium

phillips curve instability and optimal monetary policy this paper assesses the implications for optimal discretionary monetary policy if the slope of the phillips curve changes the paper first derives a phillips curve from the optimal pricing decision of a monopolistic firm that faces a changing cost of price adjustment the second aspect of the paper constructs a utility based welfare criterion a novel feature of this criterion is that is has a relative weight on output gap deviations that changes synchronously with changes in the cost of price adjustment the systematic component of the targeting rule that implements the optimal discretionary policy under the utility based criteria is constant in contrast the systematic component of the targeting rule under an ad hoc criteria changes along with changes in the slope of the phillips curve

optimal regime switching and threshold effects we consider a general control problem with two types of optimal regime switch the first one concerns technological and or institutional regimes indexed by a finite number of discrete parameter values and the second features regimes relying on given threshold values for given state variables we propose a general optimal control framework allowing to derive the first order optimality conditions and in particular to characterize the geometry of the shadow prices at optimal switching times if any we apply this new optimal control material to address the problem of the optimal management of natural resources under ecological irreversibility and with the possibility to switch to a backstop technology

the performance of forecast based monetary policy rules under model uncertainty we investigate the performance of forecast based monetary policy rules using five macroeconomic models that reflect a wide range of views on aggregate dynamics we identify the key characteristics of rules that are robust to model uncertainty such rules respond to the one year ahead inflation forecast and to the current output gap and incorporate a substantial degree of policy inertia in contrast rules with longer forecast horizons are less robust and are prone to generating indeterminacy in light of these results we identify a robust benchmark rule that performs very well in all five models over a wide range of policy preferences