on the impacts of oil price fluctuations on european equity markets volatility spillover and hedging effectiveness the objective of this paper is to investigate the volatility spillovers between oil and stock markets in europe as not all industries are expected to be equally affected by oil price changes we conduct our study at both the aggregate as well as sector levels empirically we make use of a recently developed var garch approach which allows for transmissions in volatilities in addition we analyze the optimal weights and hedge ratios for oil stock portfolio holdings based on our results on the whole our findings show significant volatility spillovers between oil price and sector stock returns and suggest that a better understanding of those links is crucial for portfolio management in the presence of oil price risk

the incremental information content of investor fear gauge for volatility forecasting in the crude oil futures market abstract this paper aims to investigate whether investor fear gauge ifg contains incremental information content for forecasting the volatility of crude oil futures for this purpose we use oil volatility index ovx to measure the ifg adding the ifg to existing heterogeneous autoregressive har models we develop many har models with ifg subsequently we employ these har models to predict the volatility of crude oil futures the results from the parameter estimation and out of sample forecasting show that the in sample and out of sample performances of har models with ifg are significantly better than their corresponding har models without ifg the results are robust in different ways thus the har models with ifg are more beneficial to the decision making of all participants including financial traders manufacturers and policymakers in the crude oil futures market more importantly the results suggest that the investor fear gauge has a significant positive effect on volatility forecasting and can help improve the performances of almost all the existing har models

effects of speculation and interest rates in a carry trade model of commodity prices abstract the paper presents and estimates a model of the prices of oil and other storable commodities a model that can be characterized as reflecting the carry trade it focuses on speculative factors here defined as the trade off between interest rates on the one hand and market participants expectations of future price changes on the other hand it goes beyond past research by bringing to bear new data sources survey data to measure expectations of future changes in commodity prices and options data to measure perceptions of risk some evidence is found of a negative effect of interest rates on the demand for inventories and thereby on commodity prices and positive effects of expected future price gains on inventory demand and thereby on today s commodity prices

information and volatility in an economy of interacting agents with both idiosyncratic and aggregate shocks we examine how the structure of private information in uences aggregate volatility the maximal aggregate volatility is attained in a noise free information structure in which the agents confound idiosyncratic and aggregate shocks and display excess response to the aggregate shocks as in lucas 14 for any given variance of aggregate shocks the upper bound on aggregate volatility is linearly increasing in the variance of the idiosyncratic shocks our results hold in a setting of symmetric agents with linear best responses and normal uncertainty we establish our results by providing a characterization of the set of all joint distributions over actions and states that can arise in equilibrium under any information structure this tractable characterization extending results in bergemann and morris 8 can be used to address a wide variety of questions linking information with the statistical moments of the economy

what drives returns to euro area housing evidence from a dynamic dividend discount model abstract we apply a dynamic dividend discount model to analyse housing returns for eight euro area countries comprising over 90 of euro area gdp both individually and as a panel a vector autoregressive model var is estimated for four variables excess return to housing rents the real interest rate and real disposable per capita income using quarterly data over the period 1978 2009 this empirical investigation which allows for a decomposition of house price movements into movements in rent cash flow and expected return news components indicates that the bulk of the variability of euro area house price movements can be attributed to movements in fundamentals there remains nonetheless an important but less sizeable influence of market wide or expected return variations in house prices country specific estimation indicates considerable heterogeneity around the euro area result both for what concerns long term impacts and dynamics notably changes in expected returns play a relatively strong role in the house prices of ireland and spain

index investment and financialization of commodities the authors found that concurrent with the rapidly growing index investment in commodity markets since the early 2000s prices of non energy commodity futures in the united states have become incr

the economic consequences of discrete recognition and continuous measurement abstract discrete recognition is a long standing and ubiquitous accounting practice but it has been widely criticized for suppressing information and inducing accounting motivated transactions we study a model to examine the economic consequences of shifting away from discrete recognition to a continuous measurement approach without manipulation discrete recognition is less informative than the continuous approach however the continuous regime induces more manipulation the equilibrium informativeness is determined by both the accounting standard and endogenous manipulation discrete recognition is more informative than its continuous counterpart precisely when manipulation is a severe threat we respond to the recent call in kothari ramanna and skinner 2010 for using positive accounting theory to explain certain long standing accounting practices we also discuss the model s implications for fair value accounting

on the links between stock and commodity markets volatility this paper investigates the links between price returns for 25 commodities and stocks over the period from january 2001 to november 2011 by paying a particular attention to energy raw materials relying on the dynamic conditional correlation dcc garch methodology we show that the correlations between commodity and stock markets evolve through time and are highly volatile particularly since the 2007 2008 financial crisis the latter has played a key role emphasizing the links between commodity and stock markets and underlining the financialization of commodity markets at the idiosyncratic level a speculation phenomenon is highlighted for oil coffee and cocoa while the safe haven role of gold is evidenced

explosive dynamics in house prices an exploration of financial market spillovers in housing markets around the world abstract asset prices in general and real house prices in particular are often characterized by a nonlinear data generating process which may display at times mildly explosive behavior in this paper using the recursive right tailed unit root test methodology proposed by phillips et al 2015a b we find widespread evidence of episodes of explosiveness or exuberance in international real house prices and establish a timeline of such episodes for a panel of 23 countries between first quarter 1975 and fourth quarter 2015 motivated by theory we adopt a dynamic panel logit probit framework to empirically investigate whether macro fundamentals and more specifically financial variables help predict such episodes of exuberance in international real house prices we find that interest rate spreads and real stock market growth together with standard housing fundamentals growth in real personal disposable income per capita and inflation are indeed among the best predictors furthermore we argue that financial developments in other asset markets can play a significant role as a trigger in the emergence of explosiveness in housing markets

foreign exchange risk pricing and equity market segmentation in africa abstract this work is the first to investigate simultaneously the occurrence of unconditional currency risk pricing and equity market segmentation in africa s major stock markets the multi factor asset pricing theory provides the theoretical framework for our model we find strong evidence suggesting that africa s equity markets are partially segmented however we find insufficient evidence to reject the hypothesis that foreign exchange risk is not unconditionally priced in africa s stock markets this result is robust to alternative foreign exchange rate adjusted return measures these findings suggest that international investors can diversify into africa s equity markets without worrying about unconditional risks associated with foreign exchange rate fluctuations

what drives commodity price booms and busts abstract we provide evidence on the dynamic effects of aggregate commodity demand shocks commodity supply shocks and storage demand or other commodity specific demand shocks on real commodity prices we analyze a new data set of price and production levels for 12 agricultural goods metals and soft commodities from 1870 to 2013 we establish that commodity demand shocks strongly dominate commodity supply shocks in driving prices over a broad set of commodities and over a long period of time while commodity demand shocks have gained importance over time commodity supply shocks have become less relevant

the relationship between energy and equity markets evidence from volatility impulse response functions this paper examines the relationship between the energy and equity markets by estimating volatility impulse response functions from a multivariate bekk model of the goldman sach s energy index and the sp in addition we also calculate the time varying conditional correlations and time varying dynamic hedge ratios from volatility impulse response functions we find that low sp however we find only a weak response from s p 500 volatility to energy price shocks moreover our dynamic hedge ratio analysis suggests that the energy index is generally a poor hedging instrument

bubbles in us regional house prices evidence from house price income ratios at the state level we investigate the presence of bubbles in the us house price income ratio at the state level by applying the recent time series based econometric test to data from january 1975 to december 2014 we

volatility impulse response functions for multivariate garch models an exchange rate illustration we introduce a new concept of impulse response functions tracing the effects of independent shocks on volatility through time while avoiding typical orthogonalization and ordering problems in an empirical study of a bivariate foreign exchange fx rate series we use volatility impulse response functions to discuss the effects of central bank decisions such as direct interventions in the fx market or open market activities on fx market volatility comparing our concept with conditional moment profiles introduced by gallant et al gallant a r rossi p e tauchen g 1993 nonlinear dynamic structures econometrica 61 871 907 we show that for shocks affecting fx rates in an asymmetric way the difference between the two methodologies and their interpretation can be substantial

oil and the macroeconomy since world war ii all but one of the u s recessions since world war ii have been preceded typically with a lag of around three fourths of a year by a dramatic increase in the price of crude petroleum this does not mean that oil shocks caused these recessions evidence is presented however that even over the period 1948 72 this correlation is statistically significant and nonspurious supporting the proposition that oil shocks were a contributing factor in at least some of the u s recessions prior to 1972 by extension energy price increases may account for much of post opec macroeconomic performance

volatility behavior of oil industrial commodity and stock markets in a regime switching environment abstract this study supplements previous regime switching studies on wti crude oil and finds two possible volatility regimes for the strategic commodity prices of brent oil wti oil copper gold and silver and the s p 500 index but with varying high to low volatility ratios the dynamic conditional correlations dccs indicate increasing correlations among all the commodities since the 2003 iraq war but decreasing correlations with the s p 500 index the commodities also show different volatility persistence responses to financial and geopolitical crises while the s p 500 index responds to both financial and geopolitical crises implications are discussed

econometric regime shifts and the us subprime bubble using aggregate quarterly data for the period 1975 q1 2010 q4 i find that the us housing market changed from a stable regime with prices determined by fundamentals to a highly unstable regime at the beginning of the previous decade my results indicate that these imbalances could have been detected with the aid of real time econometric modeling with reference to stiglitz s general conception of a bubble i use the econometric results to construct two bubble indicators which clearly demonstrate the transition to an unstable regime in the early 2000s the indicators are shown to granger cause a set of coincident indicators and financial in stability measures finally it is shown that the increased subprime exposure during the 2000s can explain the econometric breakdown i e the housing bubble may be attributed to the increased borrowing to a more risky segment of the market copyright 2013 john wiley sons ltd

u s stock returns and oil prices the tale from daily data and the 2008 2009 financial crisis abstract using daily data from january 1999 to december 2011 we examine u s stock returns s p 500 dow jones nasdaq and russell 2000 based on a wide range of information including equity vix volatility inflation expectations interest rates gold prices and the usd euro exchange rate the focus is on oil price returns which have been previously found to exert mostly negative effects on u s stock returns identifying the crisis of 2008 2009 as a significant period of economic contraction and subsequent recovery we check the stability of the stock oil relationship by garch and mgarch dcc models prior to the financial crisis stock returns are slightly negatively affected by oil prices and by the usd euro for the subsample of mid 2009 onwards however stock returns are positively affected by oil prices and a weaker usd euro as with inflation expectations we interpret these findings as u s stocks responding positively to expectations of recovery worldwide our proposed explanation is due to the changing correlation between stock markets and oil either by standard garch models or by mgarch dcc models allowing the implied correlation to vary over time

the effects of crude oil shocks on stock market shifts behaviour a regime switching approach abstract in this paper we develop a two regime markov switching egarch model introduced by henry henry o 2009 regime switching in the relationship between equity returns and short term interest rates journal of banking and finance 33 405 414 to examine the relationship between crude oil shocks and stock markets an application to stock markets of uk france and japan over the sample period january 1989 to december 2007 illustrates plausible results we detect two episodes of series behaviour one relative to low mean high variance regime and the other to high mean low variance regime furthermore there is evidence that common recessions coincide with the low mean high variance regime in addition we allow both real stock returns and probability of transitions from one regime to another to depend on the net oil price increase variable the findings show that rises in oil price has a significant role in determining both the volatility of stock returns and the probability of transition across regimes

information design bayesian persuasion and bayes correlated equilibrium abstract a set of players have preferences over a set of outcomes we consider the problem of an information designer who can choose an information structure for the players to serve his ends but has no ability to change the mechanism or force the players to make particular action choices we describe a unifying perspective for information design we consider a simple example of bayesian persuasion with both an uninformed and informed receiver we extend information design to many player and relate it to the literature on incomplete information correlated equilibrium

oil prices exchange rates and emerging stock markets abstract while two different streams of literature exist investigating 1 the relationship between oil prices and emerging market stock prices and 2 the relationship between oil prices and exchange rates relatively little is known about the dynamic relationship between oil prices exchange rates and emerging market stock prices this paper proposes and estimates a structural vector autoregression model to investigate the dynamic relationship between these variables impulse responses are calculated in two ways standard and the recently developed projection based methods the model supports stylized facts in particular positive shocks to oil prices tend to depress emerging market stock prices and us dollar exchange rates in the short run the model also captures stylized facts regarding movements in oil prices a positive oil production shock lowers oil prices while a positive shock to real economic activity increases oil prices there is also evidence that increases in emerging market stock prices increase oil prices

forecasting the volatility of crude oil futures using har type models with structural breaks abstract we introduce sixteen har type volatility models with structural breaks and estimate their parameters by applying 5 min high frequency transaction data for wti crude oil futures we find significant structural breaks in the volatility of crude oil futures additionally the historical realized volatility continuous sample path variation negative realized semivariance signed jump signed semi jump and leverage components contain substantial and salient information for forecasting the volatility of crude oil futures then we use loss functions to assess the forecasting performance of these sixteen new models and finally rank these models using the promethee ii method our results indicate that different models exhibit different predictive power in forecasting the 1 day 1 week and 1 month volatility of crude oil futures of the new har type models the new har rsv model performs best at forecasting the 1 day and 1 month volatilities whereas the new har cj best forecasts the 1 week volatility

gain loss and asset pricing we develop an approach to asset pricing in incomplete markets that bridges the gap between the two fundamental approaches in finance model based pricing and pricing by no arbitrage we strengthen the absence of arbtrage assumption by precluding investment opportunities whose attractiveness to a benchmark investor exceeds a specified threshold in our framework the attractiveness of an investment opportunity is measured by the gain loss ratio we show that a restriction on the maximum gain loss ratio is equivalent to a restriction on the ratio of the maximum to minimum values of the pricing kernel by limiting the maximum gainloss ratio we can restrict the admissible set of pricing kernels which in turn allows us to restrict the set of prices that can be assigned to assets we illustrate our methodology by computing price bounds for call options in a black scholes economy without intermediate trading when we vary the maximum permitted gainloss ratio these bounds can range from the exact prices implie

realized volatility transmission between crude oil and equity futures markets a multivariate har approach this paper differs from extant literature because it studies volatility co movements with a multivariate orthogonalized har model a flexible specification for the time series of realized volatility which is able to identify short mid and long term spillover effects we examine volatility transmission mechanisms using high frequency data of the stock index futures on s p 500 nikkei 225 ftse 100 and the futures on the west texas intermediate crude oil during the period from september 2002 to september 2012 considering the full sample the short term volatility of the equity futures contains information about future oil volatility incremental to the information inherent in the time series of oil volatility on the other hand weekly and monthly volatilities do not exhibit a significant spillover effect breaking the whole sample into three subsamples no significant granger causalities are observed in the pre crisis period while in the crisis time and its aftermath we document that the us and uk equity market volatilities to granger cause the oil futures volatility which itself leads the japanese market in terms of magnitude we observe an increase in the short term volatility spillover over time studying the residuals of the har transmission models within a ccc dcc garch framework reveals increasing instantaneous correlation between the energy and equity volatilities in the course of time

oil price shocks and stock markets in the u s and 13 european countries abstract oil price shocks have a statistically significant impact on real stock returns contemporaneously and or within the following month in the u s and 13 european countries over 1986 1 2005 12 norway as an oil exporter shows a statistically significantly positive response of real stock returns to an oil price increase the median result from variance decomposition analysis is that oil price shocks account for a statistically significant 6 of the volatility in real stock returns for many european countries but not for the u s increased volatility of oil prices significantly depresses real stock returns the contribution of oil price shocks to variability in real stock returns in the u s and most other countries is greater than that of interest rate an increase in real oil price is associated with a significant increase in the short term interest rate in the u s and eight out of 13 european countries within one or two months counter to findings for the u s and for norway there is little evidence of asymmetric effects on real stock returns of positive and negative oil price shocks for oil importing european countries

commodities price cycles and their interdependence with equity markets abstract this study examines the time scale connectedness between returns on nine african stock markets and commodities markets across energy agriculture metals and beverage first we examine multi scale short medium and long run wavelet structural relationships between african stocks and commodities using the bivariate wavelet coherence we establish that commodities and african stock returns co move across multiple scales and co integrate in the long run albeit sparse second we analyze the portfolio performance of the african stock markets with other commodities using wavelet based diversified and undiversified portfolios in a translation invariant manner to calculate the scale specific sharpe ratios over different sub periods rather than giving a one shot look for the entire sample this enables us to examine how risk adjusted returns vary across different periods the results confirm that having a combined portfolio of commodities and equities improves performance over different investment horizons specifically we observe that in non crisis periods particularly from 2001 2006 the equally weighted and optimally weighted portfolios show the greatest performances however as we enter into the crisis zones such as the asian crisis of 1997 2000 and the global financial and eurozone debt crisis the risk aversion of investors become prominent as the risk minimizing portfolios record the highest performances

dynamic spillovers between oil and stock markets in the gulf cooperation council countries this article exploits a new spillover directional measure proposed by diebold and yilmaz 2009 2012 to investigate the dynamic spillover of return and volatility between oil and equities in the gulf cooperation council countries during the period 2004 to 2012 our results indicate that return and volatility transmissions are bi directional albeit asymmetric in particular the oil market gives other markets more than it receives in terms of both returns and volatilities these trends were more pronounced in the aftermath of the global financial crisis in 2008 as the net contribution of oil has intensified after a burst during the crisis the empirical evidence from the sample is consistent with a system in which oil is playing the dominant role in the information transmission mechanism between oil and equities in the gcc countries

the theory of rational bubbles in stock prices free disposal of equity which directly rules out the existence of negative rational bubbles in stock pric es also imposes theoretical restrictions on the possible existence o f positive rational bubbles the analysis in this paper shows that a positive rational bubble can start only on the first date of trading of a stock thus the existence of a rational bubble at any date woul d imply that the stock has been overvalued relative to market fundame ntals since the first date of trading and that prior to the first da te of trading the issuer of the stock and potential stockholders who anticipated the initial pricing of the stock expected that the stock would be overvalued copyright 1988 by royal economic society

the empirical relationship between energy futures prices and exchange rates abstract this paper investigates the interaction between energy futures prices and exchange rates results are presented to show that futures prices for crude oil heating oil and unleaded gasoline are co integrated with a trade weighted index of exchange rates this is important because it means that there exists a long run equilibrium relationship between these four variables granger causality results for both the long and short run are presented evidence is also presented that suggests exchange rates transmit exogenous shocks to energy futures prices

global market integration an alternative measure and its application global markets seem to be increasingly integrated but there is no well accepted measure of integration we show that the correlation across markets is a poor measure perfectly integrated markets can exhibit weak correlation we derive a new integration measure based on the explanatory power of a multi factor model and use it empirically to investigate recent trends in global integration for most countries there has been a marked increase in measured integration over the past three decades but this is not indicated by correlations among country indexes

oil price shocks stock market economic activity and employment in greece abstract using a multivariate vector autoregression var approach this paper attempts to shed light into the dynamic relationship among oil prices real stock prices interest rates real economic activity and employment for greece the empirical evidence suggests that oil price changes affect real economic activity and employment oil prices are important in explaining stock price movements stock returns do not lead to changes in real activity and employment

forecasting the good and bad uncertainties of crude oil prices using a har framework abstract good or bad uncertainty is the volatility that is associated with positive or negative innovations to asset prices this paper proposes new heterogeneous autoregressive type har type models to forecast the good and bad uncertainties of crude oil prices in this paper we investigate the effects of lagged bad and good uncertainties daily positive and negative signed jump variations and leverages on predicting good and bad uncertainties by in sample and out of sample analysis the in sample results show that bad and good uncertainties have long memory property and the predictability of long term good and bad uncertainties is stronger than that of short and mid term good and bad uncertainties the out of sample results indicate that lagged bad or good uncertainties daily positive signed jump variation and daily negative signed jump variation contain incremental out of sample information for forecasting good or bad uncertainties and in most cases lagged leverages also play indispensable roles in forecasting the good and bad uncertainties in the crude oil market moreover the results of out of sample analysis remain robust across using the other estimation window other har type models and the other sample

volatility spillover between oil and agricultural commodity markets abstract this study examines volatility transmission between oil and selected agricultural commodity prices wheat corn soybeans and sugar we apply the newly developed causality in variance test and impulse response functions to daily data from 01 january 1986 to 21 march 2011 in order to identify the impact of the food price crisis the data are divided into two sub periods the pre crisis period 01 january 1986 to 31 december 2005 and the post crisis period 01 january 2006 21 march 2011 the variance causality test shows that while there is no risk transmission between oil and agricultural commodity markets in the pre crisis period oil market volatility spills on the agricultural markets with the exception of sugar in the post crisis period the impulse response analysis also indicates that a shock to oil price volatility is transmitted to agricultural markets only in the post crisis period this paper thereby shows that the dynamics of volatility transmission changes significantly following the food price crisis after the crisis risk transmission emerges as another dimension of the dynamic interrelationships between energy and agricultural markets

the limits of price discrimination we analyze the welfare consequences of a monopolist having additional information about consumers tastes beyond the prior distribution the additional information can be used to charge dierent prices to dierent segments of the market i e carry out third degree price discrimination we show that the segmentation and pricing induced by the additional information can achieve every combi nation of consumer and producer surplus such that i consumer surplus is non negative ii producer surplus is at least as high as pro ts under the uniform monopoly price and iii total surplus does not exceed the e cient gains from trade as well as characterizing the welfare impact of price discrimination we examine the limits of how prices and quantities can change under price discrimination we also examine the limits of price discrimination in richer environments with quantity discrimination and limited ability to segment the market

tactical allocation in commodity futures markets combining momentum and term structure signals this paper examines the combined role of momentum and term structure signals for the design of profitable trading strategies in commodity futures markets with significant annualized alphas of 10 14 and 12 66 respectively the momentum and term structure strategies appear profitable when implemented individually with an abnormal return of 21 02 our double sort strategy that exploits both momentum and term structure signals clearly outperforms the single sort strategies this double sort strategy can additionally be utilized as a portfolio diversification tool the abnormal performance of the combined portfolios cannot be explained by a lack of liquidity data mining or transaction costs

regulating a model abstract we study a situation in which a regulator relies on risk models that banks produce in order to regulate them a bank can generate more than one model and choose which models to reveal to the regulator the regulator can find out the other models by monitoring the bank but in equilibrium monitoring induces the bank to produce less information we show that a high level of monitoring is desirable when the bank s private gain from producing more information is either sufficiently high or sufficiently low when public models are more precise banks produce more information but the regulator may end up monitoring more

do structural oil market shocks affect stock prices abstract this paper investigates how explicit structural shocks that characterize the endogenous character of oil price changes affect stock market returns in a sample of eight countries australia canada france germany italy japan the united kingdom and the united states for each country the analysis proceeds in two steps first modifying the procedure of kilian kilian l forthcoming not all oil price shocks are alike disentangling demand and supply shocks in the crude oil market american economic review we employ a vector error correction or vector autoregressive model to decompose oil price changes into three components oil supply shocks global aggregate demand shocks and global oil demand shocks the last component relates to specific idiosyncratic features of the oil market such as changes in the precautionary demand concerning the uncertainty about the availability of future oil supplies second recovering the oil supply shocks global aggregate demand shocks and global oil demand shocks from the first analysis we then employ a vector autoregressive model to determine the effects of these structural shocks on the stock market returns in our sample of eight countries we find that international stock market returns do not respond in a large way to oil market shocks that is the significant effects that exist prove small in magnitude

oil price movements and stock markets revisited a case of sector stock price indexes in the g 7 countries abstract applying sector stock prices and oil prices in 1991 01 2009 05 from the g7 countries we find oil price shocks do not significantly impact the composite index in each country however stock price changes in germany the uk and the us were found to lead oil price changes as for the interaction between oil price changes and sector stock price changes we find short run negative causal relationships 4 of 7 sector index returns were impacted by oil price changes in germany 2 in the us and 1 in france in particular stock returns of information technology and consumer staples sectors were found to be impacted most by oil price shocks followed by financial utilities and transportation sectors in terms of causality from sector stock price changes to oil price changes we find stock price changes lead oil price changes in 8 of 9 sectors in germany most in the g7 countries followed by the uk italy france canada and the us no such a causal relationship however is found for japan with respect to specific sectors stock price changes in consumer staples and materials sectors were impacted most significantly by oil price changes followed by transportation financial energy health care industrials utilities information technology and telecommunication sectors with the exception of consumer discretionary sector in addition short term stock price changes are found to lead positively oil price changes

pitfalls in testing for explosive bubbles in asset prices a number of studies e g robert j shiller 1981 olivier j blanchard and mark watson 1982 kenneth d west 1988 have argued that dividend and stock price data are not consistent with the market fundamentals hypothesis in which prices are given by the present discounted values of expected dividends these results have often been construed as evidence for the existence of bubbles or fads related arguments have been made with respect to gold bonds and foreign exchange a major problem with such arguments e g james hamilton and charles whiteman 1985 is that apparent evidence for bubbles can be reinterpreted in terms of market fundamentals that are unobserved by the researcher behzad t diba and herschel i grossman 1984 1988b and hamilton and whiteman 1985 have recommended the alternative strategy of testing for rational bubbles by investigating the stationarity properties of asset prices and observable fundamentals 1 in essence the argument for equities is that if stock prices are not more explosive than dividends then it can be concluded that rational bubbles are not present since they would generate an explosive component to stock prices 2 using unit root tests autocorrelation patterns and cointegration tests to implement this procedure diba and grossman 1988b p 529 state that the analysis supports the conclusion that stock prices do not contain explosive rational bubbles this paper shows that the above battery of tests is in fact unable to detect an important class of rational bubbles the point is demonstrated by constructing rational bubbles that appear to be stationary when unitroot tests are applied even though they are explosive in the relevant sense simulations show that when such bubbles are present stock prices will not appear to be more explosive than dividends on the basis of these tests even though the bubbles are substantial in magnitude and volatility the presence of rational bubbles in actual stock prices thus remains an open question