drift in the relative price of primary commodities a case where we care about unit roots the evidence for the prebisch singer hypothesis of a downward drift over time in the relative price of primary commodities is considered the apparent strength of that evidence appears to depend to a substantial degree on whether the time series of relative prices is assumed to be trend stationary or integrated of order one moreover the usual econometric tests are relatively uninformative on this question these conclusions emerge whether or not a structural break in the series is permitted

time varying smooth transition autoregressive models nonlinear regime switching behavior and structural change are often perceived as competing alternatives to linearity in this article we study the so called time varying smooth transition autoregressive tv star model which can be used both for describing simultaneous nonlinearity and structural change and for distinguishing between these features two modeling strategies for empirical specification of tv star models are developed monte carlo simulations show that neither of the two strategies dominates the other a specific to general to specific procedure is best suited for obtaining a first impression of the importance of nonlinearity and or structural change for a particular time series a specific to general procedure is most useful in careful specification of a model with nonlinear and or time varying properties an empirical application to a large dataset of u s macroeconomic time series illustrates the relative merits of both modeling strategies

threshold effects in price transmission the case of brazilian wheat maize and soya prices recent studies into price transmission have recognized the important role played by transport and transaction costs threshold models are one approach to accommodate such costs we develop a generalized threshold error correction model to test for the presence and form of threshold behavior in price transmission that is symmetric around equilibrium we use monthly wheat maize and soya prices from the united states argentina and brazil to demonstrate this model classical estimation of these generalized models can present challenges but bayesian techniques avoid many of these problems evidence for thresholds is found in three of the five commodity price pairs investigated

rationality and deterrence this essay explores the relationship between deterrence theory and two distinct notions of rationality associated with it the author argues that the concept of procedural irrationality which is the basis of many critiques of contemporary deterrence theory is not necessarily inconsistent with the instrumental definition of rationality implicit in many models of deterrence he also argues that some recent rational choice models of deterrence are nonetheless deficient in their application of the rationality postulate finally he provides an outline of a possible resolution of the paradox of deterrence

purchasing power parity yet again evidence from spatially separated commodity markets abstract this paper examines the empirical validity of the law of one price by exploiting the non stationarity of prices set in us dollars of varieties of wheat that are traded simultaneously in the usa rotterdam and japan we demonstrate the crucial role of transport costs in achieving cointegration long run ppp although systematic short run deviations from ppp occur we show that this does not imply profitable arbitrage opportunities jel c5 f3 g1

nonlinear purchasing power parity under the gold standard 1 introductionrecent theoretical analysis of purchasing power deviations see e g dumas 1992 sercu uppal and van hull 1995 and o connell and wei 1997 demonstrates how transactions costs or the sunk costs of international arbitrage induce nonlinear adjustment of the real exchange rate to purchasing power parity ppp globally mean reverting this nonlinear process has the important property of exhibiting near unit root behavior for small deviations from ppp since small deviations from ppp are left uncorrected if they are not large enough to cover the transactions costs or the sunk costs of international arbitrage a parametric nonlinear model suggested by the theoretical literature that captures the nonlinear adjustment process in aggregate data is the exponential smooth transition autoregression model estar of ozaki 1985 a smooth rather than discrete adjustment mechanism is motivated by the theoretical analysis of dumas 1992 also as postulated by terasvirta 1994 and demonstrated theoretically by berka 2002 in aggregate data regime changes may be smooth rather than discrete given that heterogeneous agents do not act simultaneously even if they make dichotomous decisions 1 recent empirical work e g michael nobay and peel 1997 taylor peel and sarno 2001 peel and venetis 2002 has reported empirical results that suggest that the estar model provides a parsimonious fit into a variety of data sets particular for monthly data for the interwar and postwar floating period as well as for annual data spanning 200 years as reported in lothian and taylor 1996 in addition nonlinear impulse response functions derived from the estar models show that although the speed of adjustment for small shocks around equilibrium will be highly persistent larger shocks mean revert much faster than the glacial rates previously reported for linear models rogoff 1996 in this respect the estar models provide some solution to the ppp puzzle outlined in rogoff 1996 2the estar model can also provide an explanation of why ppp deviations analyzed from a linear perspective appear to be described by either a nonstationary integrated i 1 process or alternatively described by fractional processes see e g diebold husted and rush 1991 taylor peel and sarno 2001 and pippenger and goering 1993 show that the dickey fuller tests have low power against data simulated from an estar model michael nobay and peel 1997 and byers and peel 2003 show that data that is generated from an estar process can appear to exhibit the fractional property that this would be the case was an early conjecture by acosta and granger 1995 given that the estar model has a theoretical rationale whereas the fractional process is a relatively nonintuitive one the fractional property might reasonably be interpreted as a misleading linear property of ppp deviations granger and terasvirta 1999 whereas the empirical work employing estar models provides some explanation of the glacially slow adjustment speeds obtained in linear models there is one aspect of the empirical work that is worthy of further attention a second way of explaining the rogoff puzzle raised by rogoff himself 3 is to relax the assumption that the equilibrium real exchange rate is a constant see e g canzoneri cumby and diba 1996 and chinn and johnston 1996 theoretical models such as that of balassa 1964 and samuelson 1964 imply a nonconstant equilibrium in the real exchange rate if real productivity growth rates differ between countries 4 nonlinear models that incorporate proxies for these effects are found to parsimoniously fit post bretton woods data for the main real exchange rates see venetis paya and peel 2002 and paya venetis and peel 2003 naturally models that ignore this effect may generate misleading speeds of ppp adjustment to shocks in this regard the empirical results of hegwood and papell 2002 for the gold standard period are particularly interesting

on the prevalence of trends in primary commodity prices abstract this paper applies new time series procedures to examine the prebisch singer hypothesis of a secular deterioration in relative primary commodity prices specifically we allow for up to two structural breaks in 24 price series covering the 1900 98 period for the majority of commodities it is shown that the trend is not well represented by a single downward slope but instead by a shifting trend that often changes sign over the sample period unlike some recent work that has also allowed for structural breaks these results provide much less support for the prebisch singer hypothesis

trends cycles and asymmetries in the terms of trade of primary commodities from developed and less developed countries abstract the paper examines the prebisch hypothesis that primary product prices relative to the price of manufacturers fall during cyclical downturns by more than they rise during cyclical upturns and that this is an independent explanation of the secular tendency of the net barter terms of trade to move against primary commodities an important distinction is made between primary products exported by less developed countries and those exported by developed countries the greater cyclicality of primary product prices and the long run deterioration in their terms of trade since 1954 are confirmed but there is little support for the prebisch thesis that primary product prices relative to manufacturers are move sensitive on the downswing than the upswing

sets arbitrage activity and stock price dynamics this paper provides an empirical description of the relationship between the trading system operated by a stock exchange and the trading behaviour of heterogeneous investors who use the exchange the recent introduction of sets in the london stock exchange provides an excellent opportunity to study the impact of an electronic trading system upon traders who use the exchange using the cost of carry model of futures prices we estimate non linearly the transaction costs and trade speeds faced by arbitragers who take advantage of mispricing of ftse100 futures contracts relative to the spot prices of the stocks that make up the ftse100 stock index we divide the sample period into pre sets and post sets sample periods and conduct a comparative study of arbitrager behaviour under different trading systems the results indicate that there has been a significant reduction in the level of transaction costs faced by arbitragers and in the degree of transaction cost heterogeneity finally generalised impulse response functions show that both spot and futures prices adjust more quickly in the post sets period these results suggest that both spot and futures markets have become more efficient under sets

the commodity terms of trade unit roots and nonlinear alternatives a smooth transition approach market price dynamics for north american oriented strand board markets are examined specifically the role of transactions costs are examined vis a vis the law of one price weekly data for the january 3rd 1995 through april 14th 2006 period are used in the analysis nonlinearities induced by unobservable transactions costs are modeled by estimating smooth transition autoregressions stars results indicate that nonlinearity is an important feature of these markets and that the parity relationships implied by economic theory are generally supported by the star models implications for the efficiency of spatial market linkages are examined by estimating generalized impulse response functions

testing for trends in the terms of trade between primary commodities and manufactured goods abstract this paper joins the statistical debate on the terms of trade between primary commodities and manufactured goods by contributing to the methodological discussion and presenting new evidence using data series covering almost the whole of the 20th century using statistical tests that take into account breaks in the series it is found that over the 20th century the relative prices of primary commodities dropped to nearly one third of their level at the beginning of the century in two installments when random shocks led to structural breaks and not in a gradual way as implied by either a deterministic or stochastic trend possible reasons for the structural breaks and their policy implications are discussed

commodity and developing country terms of trade what does the long run show recently the debate surrounding the commodity net barter terms of trade and the terms of trade of developing countries has entered a new phase in this journal spraos i980 presents evidence of a stable declining commodity terms of trade and sapsford i985 although fl nding instability in the work of spraos argues in support of the stable declining terms of trade hypothesis grilli and yang i988 henceforth gy also provide evidence supporting this view and state the implications of this finding for developing country terms of trade a major contribution of gy is a published set of data on the main price indices with a high degree of consistency for the whole century 1 however cuddington and urzua i989 in thisjournal illustrate that the hypothesis of a secular deterioration in the commodity terms of trade is not robust to the alternative claim that there was a once and for all shift in commodity prices in the period i920 i after taking this shift into account these authors find little evidence to support the view of a secular decline 2 this debate has important implications for the prebisch singer hypothesis of a stable declining commodity terms of trade see for instance prebisch i 950 it also has implications for both development and stabilisation strategies adopted by commodity dependent developing countries a central issue in this analysis is the order of integration of the commodity terms of trade a time series is said to be integrated of order o i o if its mean and variance are constant or roughly speaking if the series is stationary a time series is said to be i n if the series requires first differencing n times before a stationary series is obtained alternatively if adding a time trend is sufficient to induce stationarity the series is termed trend stationary a trend stationary series implies that the variable in question simply adjusts around a constant growth path but an i i series is truly non stationary and displays very different properties a commonly cited example of an 1 i series is the random walk the order of integration of a single time series is related to the idea of cointegration of a number of time series consider two variables x and y that are not themselves i o but are of the same order of integration if the residuals from regressing x on y or vice versa are i o or roughly speaking if the residuals are stationary it can be concluded that the two variables are cointegrated in turn this implies that there is some form of equilibrium

long run trends in 26 primary commodity prices abstract this paper uses time series techniques to re examine the prebisch singer hypothesis that there has been a secular deterioration in primary commodity prices in terms of manufactured goods instead of using price indices it considers 26 individual commodity prices over the period 1900 1983 this avoids possible aggregation and interpretation problems associated with the use of aggregate indices the study finds that 16 of the 26 prices are trendless five have statistically significant negative trends the remaining five have positive trends it concludes that the prebisch singer hypothesis should certainly not be considered a universal phenomenon or stylized fact

trends and cycles in the net barter terms of trade a new approach this study has two objectives first it uses time series techniques including unit root tests to reexamine the classic prebisch singer hypothesis that the relative prices of primary commodities in terms of manufactured goods are characterized by secular deterioration second commodity price movements are decomposed into permanent and cyclical components using the beveridge and nelson 1981 technique the latter information is valuable when assessing the viability of commodity stabilization funds and formulating countercyclical macroeconomic policy responses to commodity booms and busts copyright 1989 by royal economic society

the law of one price evidence from the transitional economy of china abstract this paper applies the recently developed econometric methods of panel unit root tests and nonlinear mean reversion to investigate price convergence in china the largest transitional economy in the world we find that prices did converge to the law of one price in china for an overwhelming majority of goods and services based on a large panel data set the finding sheds light on the extent of the market economy in china and casts doubt on young s proposition that the economic reform has led to the fragmentation of chinese domestic markets

estimating a nonlinear rational expectations commodity price model with unobservable state variables this paper is concerned with the estimation of a model in which a possibly serially correlated stochastic process the harvest of an agricultural commodity generates a competitive price in a market comprising both final consumers and risk neutral speculators who can store the commodity at a cost in the anticipation of profit because storage cannot be negative the relationship between prices and harvests is inherently nonlinear and is an unpromising candidate for a linear quadratic model or for linearization more generally instead we calculate numerically a policy function in which price is a function of two unobservable state variables the harvest and current availability and we use the result to fit the price data

commodity prices and unit root tests price theory suggests that commodity prices should be stationary series yet tests for unit roots rather frequently imply that these prices are not stationary this seeming inconsistency is investigated by applying alternative specifications of unit root tests to prices of corn soybeans barrows and gilts and milk the preponderance of evidence suggests that nominal prices do not have unit roots but the results are sensitive to the specification of the test equation accounting for a structural change that shifts the mean appears to be an important issue in unit root tests

agglomeration and dispersion of high order service employment in the montreal metropolitan region 1981 96 much of the recent urban literature on suburban employment centres has neglected the role of high order services perhaps the principal component of edge cities in the creation of the evolving multinucleated metropolitan structure this paper specifically explores the role of high order services in this process we use employment by place of work data at the census tract level to examine the changing intrametropolitan geography of employment in four finance insurance and real estate fire services and eight business services in the montreal area over the period 1981 96 we find evidence of central business district cbd decline in relative but not absolute terms the resulting decentralisation has clearly assumed the form of polycentricity rather than of generalised dispersion in spite of recent advances in telecommunications technologies agglomeration economies continue to exert an important impact upon intrametropolitan location

time varying threshold cointegration and the law of one price a theoretical model of the law of one price which allows for seasonality in transaction costs and supply and demand conditions between markets is developed bivariate three regime threshold vector error correction models are applied to natural gas markets to examine seasonality in threshold levels results indicate that there are nonlinear adjustments to the law of one price in seven pair wise markets chicago is used as the base market in the natural gas sector dynamic threshold effects relative to the chicago market vary depending on season geographical location and whether the market is an excess producing or consuming market

exchange rates and traded goods prices abstract this paper presents a partial equilibrium model of the determination of domestic and export prices by a monopolistic competitive firm the model stresses the role of exchange rate uncertainty and expectations the most important result of the analysis is that the stochastic properties of deviations from the law of one price are crucially affected by the currency of denomination of export prices using data on domestic and dollar export prices of japanese goods i find that deviations from the law of one price are due to exchange rate surprises but also to price staggering and ex ante price discrimination

evidence on purchasing power parity from univariate models the case of smooth transition trend stationarity recent research has found that trend break unit root tests derived from univariate linear models do not support the hypothesis of long run purchasing power parity ppp for us dollar real exchange rates in this paper univariate smooth transition models are utilized to develop unit root tests that allow under the alternative hypothesis for stationarity around a gradually changing deterministic trend function these tests reveal statistically significant evidence against the null hypothesis of a unit root for the real exchange rates of a number of countries against the us dollar however restrictions consistent with long run ppp are rejected for some of the countries for which a rejection of the unit root hypothesis is obtained

commodity prices and growth in africa a frican economies export primary commodities and most export little else policymakers as well as economists and historians of african economic development have seen these exports as both a hope and a curse the following parable tells the story once upon a time a servant of the ruler discovered a miraculous plant which grew readily in that country and whose seeds could be woven into fine cloth so desirable was this fabric that it became prized all over the world and fetched a high price after two score years the plant accounted for most of the country s trade with the world the ruler ordered the peasants to grow the plant paid them only a fraction of its price and he and his nobles became fabulously wealthy because the ruler wished to be remembered as a great ruler and as the father of his country he used his wealth to build a great army and brought machines from foreign countries to make the fine goods that previously could only be obtained from foreign merchants but the machines often broke down and the goods that they made were of poor quality and after the ruler died they were left to rust under the ruler s successor there was a war in a foreign land where the plant also grew so that there was a great shortage and its price increased threefold in only three seasons the new ruler spent his newfound riches on fantastic extravagance while immense sums were expended on public works after the manner of the east and on productive works carried out in the wrong way or too soon not even the threefold increase in prices could support these expenditures and the country soon found itself deeply in debt when the war ended and the price fell the country could no longer pay the interest on its debt or borrow more money even after it had sold its only useful public work to a foreign power so that power sent a mission to the country the publication of whose report from which the above

the statistical debate on the net barter terms of trade between primary commodities and manufactures a comment and some additional evidence i950 p s hypothesis according to this hypothesis the net barter terms of trade nbtt between primary products and manufactures have over the longrun exhibited a downward trend spraos presented a detailed and thorough analysis of both the adequacy of the various statistical series available to proxy the nbtt s behaviour over the long run and the wide range of conceptual including quality problems involved in such an exercise on the basis of his analysis spraos concluded that the balance of the evidence for the seventy year period ending with the outbreak of world war ii supported the p s hypothesis of a secular deterioration in the nbtt it should however be noted that the evidence also suggested that the particular series cho sen for analysis by prebisch i950 himself did appear to exaggerate possibly to a large extent the rate of deterioration however when the analysis was extended to include the post world war ii period spraos found that while the deteriorating tendency cannot be decisively refuted it is open to doubt when the record up to the i970s is taken into account i980 p i26 as we shall see in this paper closer scrutiny reveals a statistical problem with spraos s analysis and the purpose of this paper is to show that once appropriate action is taken to overcome this problem some quite strong evidence in support of the p s hypothesis emerges the paper is organised as follows section i briefly discusses spraos s methodology and section ii discusses an econometric issue arising from this analysis section iii presents our empirical evidence while section iv summarises the main findings of the paper

spatial market integration in the presence of threshold effects a large body of research has evaluated price linkages in spatially separate markets much recent research has applied models appropriate for nonstationary data such analyses have been criticized for their ignorance of transactions costs which may inhibit price adjustments and thus affect tests of integration this analysis utilizes threshold autoregression and cointegration models to account for a neutral band representing transactions costs we evaluate daily price linkages among four corn and four soybean markets in north carolina nonlinear impulse response functions are used to investigate dynamic patterns of adjustments to shocks our results confirm the presence of thresholds and indicate strong support for market integration though adjustments following shocks may take many days to be complete in every case the threshold models suggest much faster adjustments in response to deviations from equilibrium than is the case when threshold behavior is ignored a large amount of empirical research has evaluated the extent to which spatially separate markets are integrated though the term is used loosely in the literature tests of market integration usually consider the extent to which shocks are transmitted among spatially separate markets the integration of markets can have important implications for price discovery and the operation of the market since persistent deviations from integration may imply riskless profit opportunities for spatial traders

the prebisch singer hypothesis a reappraisal independent of stationarity hypotheses time series behaviour of the relative price of primary commodities raul prebisch i950 and hans singer i950 believed that the long term trend of primary commodity prices was negative the latter in an interesting discussion of the above quandary pp 482 3 viewed rises in primary commodity prices as purely temporary sources of surplus that offered short lived opportunities to increase industrial investment these opportunities were missed by private investors who instead increased primary sector investment in such circumstances because all private activity tends to be governed by the price

spatial market arbitrage and threshold cointegration goodwin and piggott reported that corn and soybean prices in spatially separated markets in north carolina exhibited threshold cointegration and that commodity prices in different markets may persistently diverge here a multivariate approach is used to test for threshold cointegration and nonlinear cointegration the results suggest that departures from the law of one price do not persist indefinitely goodwin and piggott gp examined daily corn and soybean prices across spatially separated markets in north carolina and reported that bivariate pairings of prices were threshold cointegrated gp used a twothreshold model in which price differences across markets could persist indefinitely they concluded that empirical models should consider threshold effects in order to adequately characterize spatially integrated markets the purpose of this article is to extend the gp analysis in several directions gp employed the techniques of martens kofman and vorst which involve a multistepped search for thresholds in the residuals of a cointegrating regression this single equation search process is subject to potential misspecification so it is interesting to determine whether the direct multivariate test of threshold cointegration of hansen and seo provides confirmatory evidence in addition gp allowed two thresholds to affect each commodity pair without directly testing for the number of thresholds the second extension uses hansen tests to determine the number of thresholds two thresholds imply no arbitrage bounds that allow persistent departures from the law of one price one threshold is consistent with the traditional view that price differentials are fleeting as arbitrageurs drive excess returns to zero the final extension recognizes that spatially integrated markets might follow a nonlinear relationship that depends on transactions costs peter s sephton is professor school of business queen s university kingston ontario canada the author would like to thank nick piggott for providing his dataset and the dean s research fund in the school of business for financial assistance two anonymous referees provided helpful comments sufficiently large deviations from the law of one price should lead to a reduced price dispersion a direct test of nonlinear cointegration demonstrates that price differences tend to be resolved over time background