Shocks to food market systems: A network approach

In order to better understand how cross-border price shocks are transmitted to domestic food markets, we augment an error correction model with a network approach and apply it to Tanzania. We show the following. First, Dar es Salaam, Tanzania's largest city and port, is not a significant influence. Second, demand shocks emanate primarily from border markets that may serve as conduits for informal trade. Third, market linkages differ considerably across seasons and commodities. Fourth, prices in areas with high production potential are especially sensitive to systemic shocks. More broadly, we show that a network approach in conjunction with time series analysis can enhance our understanding of the origins and channels through which shocks are transmitted to food markets.     

Price shock transmission: evidence from the wheat‐bread market value chain in Ethiopia

This study assesses the degree of vertical price transmission along the wheat‐bread value chain in Ethiopia. This is pursued by applying a vector error correction model and an impulse response analysis using monthly price data for the period 2000–2015. Our analysis considers transmission of price shocks across different market levels, including from the international and domestic wheat grain markets at the upstream to the domestic wheat bread market at the downstream of the value chain. The empirical findings indicate that significant cointegration exists across prices of the different market stages. There is a transmission from international prices to domestic prices at downstream markets, in particular to flour and bread prices. Prices at upstream markets are largely influenced by the domestic wholesale market. In general, the speed of adjustment is quite slow with a half‐life of about one year for restoring the equilibrium price relationship. As price margins between the different market stages in the value chain have substantially decreased in the last 15 years, higher transmission, and thus exposure to international market shocks, can be expected in the future. The results also show that causal relationships exist between prices at different market stages—with the wholesale market identified as the key market level where prices and price expectations are formed.     

Regional Integration of Nineteenth Century U.S. Egg Markets

Multivariate asymmetric threshold vector error correction models are applied to a historical analysis of the regional integration of U.S. markets for eggs at the turn of the nineteenth century. Two general approaches to the selection of the thresholds are considered. The first criterion ignores the cross equation correlation while the latter explicitly accounts for it. Our results suggest that threshold behaviour characterises spatial price linkages between the markets analysed.     

Relationships between U.S. and Canadian Wheat Prices: Cointegration and Error Correction Approach

This paper examines relationships between U.S. and Canadian wheat prices using the cointegration and error correction approach. The use of the error correction model is appropriate because U.S. and Canadian wheat prices are first-differenced stationary and cointegrated. The results suggest that both U.S. durum and hard spring wheat prices respond to restore equilibrium relationships with the corresponding Canadian price, while the Canadian prices do not. That is, the structure of the respective policies is such that the Canadian markets are largely insulated from influences flowing directly from the U.S., while U.S. markets are not insulated from Canadian influences. These results could be interpreted to support the contention that Canadian production subsidies and the implicit export subsidies would tend to undermine the U.S. price support program. The results also support the price leadership role for Canada in the durum and hard spring wheat markets. The implication is that with respect to durum and spring wheats, U.S. policies to artificially support domestic prices are not effective over the long run. Les rapports entre les prix de blé canadiens et américains sont étudiés á partir des analyses basées sur la cointégration et la méthode de correction des erreurs. L'emploi de la méthode de correction des erreurs est approprié car les prix de blé canadiens et américains sont cointegres et stationnaires quand Us sont exprimes en changements (first differences). Les résultats montrent que les prix du blé dur (durum) et du blé panifiable du printemps (hard spring) aux États- Unis reagissent à l'évolution des prix canadiens pour retablir le rapport d'équilibre tandis que ceux du Canada ne sont pas influencés par les désequilibres. Ce résultat est explique par les differences entre les structures des politiques agri-coles quifont que les marches canadiens sont largement isoles des influences en provenance des États-Unis, ce qui n'estpas le cas pour les marches américains. Ces résultats pourraient vouloir dire que des subventions canadiennes à la production et à l'exportation ont mine les programmes américains de sou-tien des prix. Us sont également compatible avec l'idée que le Canada établit les prix sur ces marchés.     

Spatial Integration of Wheat Markets in India: Evidence from Cointegration Tests

Using the maximum likelihood method of cointegration, this paper empirically evaluates intra-state and inter-state spatial integration of wheat markets in India. The cointegration tests provide strong evidence in favour of spatial integration of the regional wheat markets. Even though the regional markets are geographically dispersed, the prices across different market centres within and across the selected states have exhibited long-run spatial linkages, suggesting that all the exchange locations are integrated and the prices provide relevant market signals. There are several implications of these results for agricultural price policy and food market liberalization programmes.     

The Spatial Integration of Paddy Markets in Vietnam

This paper examines whether there is spatial integration between and within paddy markets in the north and south of Vietnam. The empirical model developed uses estimates of transfer costs to generalise Ravallion's model of spatial market integration to allow for threshold effects. A sequential testing strategy is used to test for market segmentation, the number of thresholds, long‐run integration, informational efficiency and the Law of One Price within an error‐correction framework. We find neither threshold effects nor weak evidence of paddy market integration between northern and southern Vietnam. There is, however, evidence of both threshold effects and stronger market integration within the Red and Mekong River deltas. Whenever price spreads exceed their thresholds, at least 60% of price changes are transmitted between regional markets within a month. Nonetheless, the instantaneous version of the Law of One Price only holds for a few regimes and market pairs. These results suggest that national level policies cannot be relied upon to stabilise or support paddy prices in Vietnam. Instead, policies need to be designed with the specific production, consumption and marketing characteristics of northern and southern Vietnam in mind.     

Assessing the Vulnerability to Price Spikes in Agricultural Commodity Markets

We examine empirically the predictability of conditions associated with a higher probability of a price spike in agricultural commodity markets. We find that the forward spread is the most significant indicator of probable price jumps in maize, wheat and soybeans futures markets, a result which is in line with the ‘Theory of Storage’. We additionally show that some option-implied variables add significant predictive power when added to the more standard information variable set. Overall, the estimated probabilities of large price increases from our probit models exhibit significant correlations with historical sudden market upheavals in agricultural markets.     

Optimal Protein Segregation Strategies for Wheat Growers

A technology that can measure wheat grain protein concentration and then segregate grain based on measurements during harvesting is on the horizon. This new technology provides wheat growers with opportunities to segregate grain that can be directed to premium markets. In this article, we identify an individual grower's optimal segregation and blending strategies under non‐uniformly curved price schedules. When price schedules are three‐step shaped, we show that the optimal segregation and blending strategies can be obtained by solving a specified non‐linear programming problem. Based on cash price and protein distribution data for wheat in the U.S. Pacific Northwest region over 1991–2011, an application of our theoretical model shows that on average a Hard Red Winter (respectively, Hard Red Spring) wheat grower should be willing to pay about 17.7 (respectively, 30.8) cents for segregating one bushel of wheat. We also study how growers’ net returns would be affected were the technology to be adopted.     

The Extent, Pattern, and Degree of Market Integration: A Multivariate Approach for the Brazilian Rice Market

The extent, pattern, and degree of integration are analyzed in a multivariate system with cointegrating restrictions. The extent of the market is found by identifying locations that are linked by trade and where prices share identical long run information (permanent component). The pattern of integration characterizes interdependence and is analyzed by estimating a vector error correction model. The degree of integration is calculated with persistence profiles of the long run relations. We demonstrate that bivariate models are inadequate for capturing the spatial dynamics of price adjustment. The methodology is applied to the Brazilian rice market and policy implications are discussed.     

Wheat stocks and the cointegration of wheat prices

We examine the effect of wheat stocks on the relationship between port and inland wheat prices in western Canada after the dissolution of the Canadian Wheat Board in 2012. Standard statistical tests find no evidence that the port price is cointegrated with inland prices. We argue that large harvests in 2013–2014 and 2014–2015 are responsible for this lack of cointegration. A simple theoretical model demonstrates how wheat stocks drive a wedge between inland and port prices. After including wheat stocks in the cointegrating vector, we find the expected cointegrating relationships between the port and inland prices. Using an error correction model, we show that a 10% increase in the wheat stocks reduces producer prices in Alberta and Manitoba by 6% and 4%, respectively. We conclude by discussing policy options for reducing the size of wheat stocks on the prairies.     

Estimating Policy Effects on Spatial Market Eff iciency: An Extension to the Parity Bounds Model

The standard parity bounds model (PBM) is extended to allow for dynamic shifts in regime probabilities in response to changes in marketing policy. The approach allows estimation of the length of the adjustment period and a statistical test for no policy effects. The extended PBM is applied to maize and wheat markets in Ethiopia. Evidence of a dynamic adjustment path is found and grain marketing reforms are found to have improved spatial efficiency in a few markets, worsened it in a few others, but generally to have had little effect on the spatial efficiency of Ethiopian grain markets.     

Price relationships between qualitatively differentiated agricultural products: organic and conventional wheat in Germany

Organic agriculture, which produces commodities that can be qualitatively differentiated from conventional food products, has grown into an important market in many countries. The dynamics of commodity prices in both sectors are partly interdependent, but are also shaped by independent determinants and have rarely been studied. We analyze organic food markets and their interdependencies with conventional markets in the context of wheat markets in Germany, which have been subject to a number of fundamental changes during the last two decades. Based on institutional market characteristics, we suggest a flexible Markov‐switching asymmetric time series model. We find a pronounced temporal sequence of market phases that differ in their asymmetric dynamics and the extent to which the organic price is influenced by the conventional price. Organic wheat prices tend to be increasingly connected to prices of conventional wheat.     

A quantile autoregression analysis of price volatility in agricultural markets

This paper investigates the dynamics of agricultural price volatility based on a quantile autoregression (QAR) model. The QAR model provides a flexible representation of the distribution of price and its dynamics. The approach is applied to U.S. wheat and corn markets over the period of 1980–2017. This period is of significant interest as it covers important changes in agricultural policy and increased reliance on markets. The price analysis is conducted conditional on stocks held in the previous period. We show how increasing previous stocks shift the price distribution to the left and decreases the odds of facing price spikes (by shifting down the upper tail of the price distribution). Our analysis also examines the effects of changing public stocks on prices. For both wheat and corn, this reflects changing agricultural policy, contrasting the 1980s (when public stocks were relatively high) with the post-2005 period (when public stocks became zero). We document how higher public stock ratio during the previous period did not lower the odds of facing price spikes. Applied to the wheat and corn markets, we also uncover evidence of local dynamic instability in the upper tail of the price distribution, suggesting that price instability becomes more pronounced when previous stocks are low.     

Spatial price efficiency in Mozambique's post-reform maize markets

Maize (Zea mays) shortages and maize price instability continue to occur in Mozambique in spite of policy reforms and great capacity for increased production in northern Mozambique. This study measured the efficiency of spatial maize price arbitrage in Mozambique's post‐reform period. Spatial price inefficiency does not seem to explain why food shortages continue to occur in Mozambique, suggesting nonprice market constraints such as poor infrastructure and poor market institutions as more likely explanations. Baulch's spatial efficiency test indicated that it is not profitable to ship maize from northern surplus maize regions to southern Mozambique. Records of interregional maize shipments show that indeed grain is not being shipped from the north to the south. Market liberalization may have improved spatial price efficiency, but high transfer costs still limit trade and potential benefits from freeing markets. Under these circumstances, food shortages and price instability are likely to continue.     

农产品垂直价格传递与纵向市场联结

本文分析了我国主要农产品市场垂直价格传递和纵向市场联结的关系。我国农产品市场的两类纵向联结形式以契约市场为准则建立的松散型联结和以产权一体化(或功能层级化)建立的紧密型联结。建立非对称纵向价格传递的误差修正模型(APT-ECM)对四类主要农产品市场的实证分析表明,纵向市场联结越松散(契约型),非对称垂直价格传递特征越微弱;纵向市场联结越紧密(层级型),非对称垂直价格传递特征越明显。     

Testing vertical price transmission for Vietnam's Robusta coffee

Vietnam has undergone market reforms over the last three decades; and as a consequence, the coffee sector has become increasingly market‐driven. The success of the government's liberalisation policies in terms of market efficiency is investigated by examining the transmission of both positive and negative price changes for Robusta coffee between export and farmgate prices. We used a threshold vector error correction model and high‐frequency daily data. The primary result here is that of a symmetric price transmission between export and farm‐level prices. This result holds when tested with weekly price data, derived from the daily data. Farmgate prices respond faster to decreases than increases in export prices when the long‐run deviation exceeds a certain threshold. These price changes are transmitted within several days. This research also confirms the importance of transaction costs, and other price frictions mostly ignored in prior analyses for coffee.     

Buyer Collusion and Efficiency of Government Intervention in Wheat Markets in Northern India: An Asymmetric Structural Auctions Analysis

This article uses auction theory to analyze wholesale markets for wheat in Northern India. This approach enables us to characterize the market in terms of buyer asymmetries, to detect the existence of collusion, and to quantify its impact on market prices. We show that buyer asymmetries exacerbate the downward impact of collusion on prices. The article also considers whether the government paid too much for the wheat it procured at the minimum support price, and shows that for our sample it did not. The article is based on a primary survey of two wholesale markets in North India.     

Export Restrictions and Smooth Transition Cointegration: Export Quotas for Wheat in Ukraine

We extend previous modelling approaches to identify domestic price effects of export controls. We allow for smooth transition between free‐trade price transmission regimes and those under export restricting regimes, using a smooth transition cointegration (STC) approach, rather than the more common assumption that regime changes are abrupt. Our approach has the advantage that the switch in the price transmission regime may be induced not only by an actual but also by an expected policy change. Results confirm the gradual nature of the transition between the regimes, which reflect trader heterogeneity and wheat storage decisions. We find that the STC approach outperforms alternative model approaches in terms of both regime classification and goodness of fit, when explaining Ukrainian domestic wheat prices under export controls. In particular, application of the Markov‐switching error correction model (MSECM) to the same data generates results which do not reflect any identifiable economic reality (in contrast to Götz et al., 2013 ).     

Black Sea and World Wheat Market Price Integration Analysis

In 2008–10, Russia and Ukraine together exported an average of 29 million tons of wheat per year, and have become important players in the international wheat market. This research summarizes the short‐ and long‐run wheat price dynamics between Ukraine and Russia, and other major wheat exporters—the United States, European Union (EU), and Canada—from 2004 to 2010. Tests of market price co‐integration (Johansen maximum likelihood test and residual‐based tests) as well as threshold error correction techniques were performed for this purpose. The results suggest that Russian wheat prices were co‐integrated with EU and U.S. wheat prices but not with Canadian wheat prices. Ukrainian wheat prices were found to be co‐integrated with French wheat prices only. The estimated long‐run wheat price transmission elasticities were estimated to be equal to 1.04 between Russian and French (a representative country of the EU) wheat prices, 1.16 between Russian and U.S. wheat prices, and 1.05 between Ukrainian and French wheat prices. We also found the short‐term relationships between the co‐integrated series to be statistically significant. Price adjustments in all co‐integrated prices were found to be symmetric.     

Market interdependence and volatility transmission among major crops

This article provides a comprehensive analysis of the dynamics of volatility across major agricultural commodities in the United States. Volatility interactions across markets may lower the effectiveness of diversification strategies to mitigate price risks and should be taken into account when analyzing the pricing behavior of different agricultural commodities. We follow a multivariate GARCH approach to evaluate the time evolution of conditional correlations and volatility transmission across corn, wheat, and soybeans price returns on a daily, weekly, and monthly basis. The period of analysis is from 1998 to 2012. The estimation results indicate a lack of lead‐lag relationships between corn, wheat, and soybeans price returns at the mean level. We find, however, important volatility spillovers across commodities, particularly at the weekly and monthly level. Wheat and corn seem to play a major role in terms of volatility transmission. Despite the supposed higher financial market integration of agricultural commodities, we do not observe that agricultural markets have become more interdependent in recent years.