What Does Granger Causality Prove? A Critical Examination of the Interpretation of Granger Causality Results on Price Effects of Index Trading in Agricultural Commodity Markets

The influence of index trading on price levels, returns, spreads or volatility in agricultural commodity markets is frequently investigated with bivariate Granger Causality (GC) tests. A joint review of existing empirical studies reveals scant and inconsistent evidence of GC from index activity to prices. Some findings of reverse GC from prices to index activity are reported. The literature offers three different interpretations of GC test results: (i) as prima facie causal evidence; (ii) as a test for informational efficiency of the markets; or (iii) as a test for the ability of one variable to improve the forecast of another variable. A critical examination of these interpretations against an extended theoretical background reveals that none allows direct inferences about the existence or absence of an influence from index trading activity on the price mechanism in the market. This severely limits the usefulness of a stand‐alone application of GC tests.     

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.     

Middlemen behaviour and generic advertising rents in competitive interrelated industries

This article focuses on the role of middlemen in determining the returns to generic advertising in a competitive industry where supply is uncontrolled, the price of marketing inputs is endogenous, and retail markets are interrelated through consumer preferences. Theoretical analysis suggests farm-gate returns (quasi-rents) are overstated when input substitution at middlemen level is ignored, a result confirmed in the empirical application. As for mark-up behaviour, represented by the farm-retail price transmission elasticity, a general result is that farm-gate returns to generic advertising always increase as the transmission elasticity decreases, provided retail demand is more elastic than input substitution. Endogenising the price of marketing inputs has little effect on advertising rents.     

The Role of Index Trading in Price Formation in the Grains and Oilseeds Markets

We use both Granger‐causality and instrumental variables (IV) methods to examine the impact of index fund positions on price returns for the main US grains and oilseed futures markets. Our analysis supports earlier conclusions that Granger‐causal impacts are generally not discernible. However, market microstructure theory suggests trading impacts should be instantaneous. IV‐based tests for contemporaneous causality provide stronger evidence of price impact. We find even stronger evidence that changes in index positions can help predict future changes in aggregate commodity price indices. This result suggests that changes in index investment are in part driven by information which predicts commodity price changes over the coming months.     

A speculative bubble in commodity futures prices? Cross‐sectional evidence

Recent accusations against speculators in general and long-only commodity index funds in particular include: increasing market volatility, distorting historical price relationships, and fueling a rapid increase and decrease in the level of commodity prices. Some researchers have argued that these market participants—through their impact on market prices—may have inadvertently prevented the efficient distribution of food aid to deserving groups. Certainly, this result—if substantiated—would counter the classical argument that speculators make prices more efficient and thus improve the economic efficiency of the food marketing system. Given the very important policy implications, it is crucial to develop a more thorough understanding of long-only index funds and their potential market impact. Here, we review the criticisms (and rebuttals) levied against (and for) commodity index funds in recent U.S. Congressional testimonies. Then, additional empirical evidence is added regarding cross-sectional market returns and the relative levels of long-only index fund participation in 12 commodity futures markets. The empirical results provide scant evidence that long-only index funds impact returns across commodity futures markets.     

Financial drivers of land use decisions: The case of smallholder woodlots in Amhara,Ethiopia

A household survey on the financial drivers of woodlot production was conducted in the Lake Tana watershed of Amhara State, Ethiopia. Analysis of smallholder Eucalyptus globulus Labill. production reveals that converting uneroded over eroded croplands leads to significantly higher financial returns. Returns were also significantly higher for rotation intervals closer to the optimal economic rotation and for higher planting densities. Most woodlots had positive financial returns. The presence of negative financial returns for some households demonstrates that positive ecological externalities, a lack of economies of scale and/or myopic behavior are potentially important factors in land use decision-making. Wood utilization decisions were shown to impact the potential financial returns of households. Smallholders’ activities demonstrate that eucalyptus is an imperfect substitute for agricultural production on surplus cropland. A third of respondents indicated they had intentionally chosen to convert uneroded croplands to achieve higher returns. Smallholders faced constraints in bargaining over price and access to markets. Future land use policies should address marketing constraints and unsustainable land use activities. Harvesting soil from natural forests and the conversion of productive surplus cropland to woodlot production both present long-term sustainability challenges. This study demonstrates the importance of considering economic and social incentives when creating land use policies for smallholder's woodlot production.     

Comovement of dairy product futures and firm value: returns and volatility

This study investigates the exposure of dairy firm stock prices to the prices of dairy product futures, in terms of returns and volatility, from May 2013 to April 2018. Stock price returns are regressed against an index of the futures price returns to four dairy products – milk, cheese, butter and dry whey – to isolate the effects of the dairy futures price returns. Dairy product futures price returns are found to be significant in the regression in the first three years of the sample period, with a mean coefficient of ?0.024. Using the Diebold‐Yilmaz volatility spillover method of forecast error variance decomposition, we show that the volatility of the four dairy product futures accounted for an average of 5.49 per cent of the volatility of dairy stock prices. These results suggest that the prices of dairy firms have minimal exposure to dairy product futures prices. This has implications for dairy firms and investors, who seek to understand volatility and returns in the dairy products and the stocks they trade in, and for policymakers, who seek to control or mitigate undesirable dairy product price volatility.     

MARKETING AGENCIES AND THE ECONOMICS OF MARKET SEGMENTATION*

Increasing importance is being attached to market segmentation strategies as a means of increasing producer returns. In this paper, a generalised model of price discrimination without supply control is developed to analyse the implications of optimal segmentation strategies for non-homogeneous products. It is shown that the magnitude of producer returns is dependent on demand and supply conditions, with increases in returns falling as price elasticities of demand and supply increase. The model is applied to the New Zealand sheep meats industry to reveal that returns to producers from market segmentation strategies could be quite low in the long run.     

Price Transmission in Nigerian Food Security Crop Markets

This paper comprehensively examines price transmission from world, neighbour country, and internal commercial hub markets to Nigerian urban markets, as well as from urban to rural markets within the country, for seven key food security crops (maize, millet, sorghum, rice, cassava, yams and cowpeas). There are three key findings: (i) tradability matters for price transmission, but tradability varies across crops and regions. The strongest international linkages are with neighbouring countries. Rice price transmission is high across all markets, while coarse grain price correspondence is low with world prices but high with neighbour country market prices; (ii) our results imply that local conditions matter for price transmission, and are relatively more important than trade for some crops (e.g. yams, cassava) than others (e.g. imported rice, maize); (iii) larger than expected long‐run price transmission parameters in world and neighbour countries for rice and coarse grains suggest that, in these select markets, there are either large transactions costs or quality premiums that vary systematically with border prices, and/or mark‐ups captured by traders with market power.     

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.     

Intra-annual sheep price patterns and factors underlying price variations in the central highlands of Ethiopia

A sheep market survey was undertaken to determine the effects of certain animal and market characteristics on price and the pattern of sheep prices in relation to seasons. Nine key Ethiopian central highlands markets were surveyed for a period of one year in 1989. Each market was surveyed once a week on the main market day. Price, weight, sex, age, colour, condition score, breed type and buyer's purpose were recorded for all completed transactions as well as the numbers offered and sold on each market day. A total of 50062 cases were recorded. Three markets, each representing redistributive, intermediate and terminal markets, as identified by the distribution in buyer's purpose were chosen for further analysis. Considerable weekly price variation was evident in these markets. Prices were also seasonal with higher premiums paid during some religious festivals. Animal characteristics (weight, age, condition, sex, colour) as well as buyer's purpose and seasons were variably important in explaining variation in price among animals within weeks. Variations in the composition of these characteristics from week-to-wcek were among factors underlying changes in weekly mean prices. R² varied from 0.2659 to 0.3583 in the quadratic price per kg model and from 0.7822 to 0.8413 in the quadratic price per head model in the three markets. However, it was found that price per head was predicted equally well overall by estimated price per kg multiplied by actual weights and that because of wide variation in weights, both within and between weeks, price per kg is more useful market information.     

Agricultural price transmission elasticity: importance of controlling for unobserved common factors

A voluminous amount of the literature estimates price transmission from world markets to domestic markets ignoring unobserved factors that commonly affect domestic markets. This article reevaluates the long‐run and short‐run transmission elasticity of world food price shocks to domestic markets using a “common factor framework” that takes unobserved common factors that are correlated with regressors into consideration. In the estimation, annual price data for rice, wheat, and maize for a panel of developed and developing countries that are observed over the period of 1960–2007 are used. The results from a common factor framework to those that do not account for common factors are then compared. Our findings suggest that ignorance of common factors is likely to result in upwardly biased elasticity estimates.     

Price Discrimination in the Context of Vertical Differentiation: An Application to Canadian Wheat Exports

The ability of the Canadian Wheat Board (CWB) to price discriminate in wheat exports is examined. The conceptual model shows that the CWB's ability to exploit cost differences in pricing depends on the extent of differentiation between Canadian and U.S. wheat. This model is implemented using monthly confidential price data for exports to four markets from 1982 to 1994. The empirical results support the conclusions that (1) the CWB has market power emerging from product differentiation, (2) the CWB price discriminates across export markets, and (3) Alchian–Allen effects are important in pricing in markets valuing quality such as Japan and the United Kingdom.     

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.     

中国碳排放权交易市场收益率波动性特征研究

以北京、上海、广东、湖北和重庆碳排放权交易市场为研究对象,运用GARCH族模型研究中国碳排放权交易市场收益率波动性特征。结果表明,5个碳排放权交易市场收益率的波动聚集性、持续性表现不完全一致;北京、上海和重庆存在负向的杠杆效应,广东和湖北不存在杠杆效应;从波动溢出效应关系看,5个碳排放权交易市场间的整体联动性不强;运用方差比率检验法得出,5个碳排放权交易市场均未达到弱势有效市场。这些特征反映出中国碳排放权交易市场的运行机制仍然存在缺陷,建议加强顶层设计,完善碳排放权交易体系。     

Are We Moving Towards Functioning Agricultural Markets and Trade Relations?

We introduce a special feature on the functioning of international agricultural markets. This feature is motivated by the increased interest in the functioning of commodity markets raised by unprecedented price turbulences since 2008, major structural changes through changed roles of emerging economies and related concerns regarding food security. We argue that the delineation of non‐functioning markets from markets that adequately adjusted to adverse framework conditions lacks theoretical foundation. We discuss the relevance of some results on institutions for agricultural markets in emerging and transition countries. A synthesis of the articles included in the special feature is provided by highlighting the selection of topics that span a topical range covering price formation on world and domestic markets, market power and trade policy modelling.     

Ride the trend: Is there spread momentum profit in the US commodity markets?

Some previous researchers have argued that trading strategies based on calendar spread time series momentum (STSM) can deliver significant returns (Szymanowska et al. 2014; Boons and Prado 2019), which, if true, is at odds with the efficient market hypothesis. These arguments however, do not exclude the unrealisable futures contract roll yield and are also affected by other empirical and statistical issues that may lead to misleading results. With more than 30 years of data, we investigate STSM in 22 US commodity futures markets. First, we assess whether past spread returns can predict future returns, a necessary condition for the existence of momentum. We find predictability to be very weak after correcting for the issues affecting prior research. Second, we implement STSM-based investment strategies. We compare STSM profits for individual markets and portfolios to profits generated by a simple long-only benchmark strategy that does not require any predictability. STSM does not generate returns statistically different from the benchmark trading strategy, with both strategies generating very low or negative returns. For the momentum to outperform the benchmark strategy, predictability should be three times larger than observed from real data, but would entail substantial downside risk. In sum, the empirical evidence indicates that returns from STSM-type strategies are illusive for the commodities and period studied. Our results strongly suggest that inclusion of unrealisable roll yield generates the illusion of profitable STSM trading strategies in previous research.     

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.     

Price anomalies and effectiveness of macro control policies: Evidence from Chinese housing markets

Since the housing market reform in 1998, China has experienced a rapid growth. Continuous surges in housing prices have been criticized by the public. In light of deviation of the price from its intrinsic value, the central government implements a series of policies to intervene the housing market, but makes little difference. Little vigorous academic work on the price anomaly and impact of macro-control measures has been conducted for housing markets in urban China. This research employs econometric methodologies to investigate the interactions between housing price and market fundamentals, in order to identify the existence of price anomaly in the housing markets of Beijing and Shanghai during 1998–2012. In addition, we conduct asymmetry analysis based on an advanced econometric model to investigate the impact of macro-control measures on price and volume. Our findings suggest that the market inefficiency is indicated by lack of interaction between housing supply and demand in Beijing and Shanghai. The opposite directions of impulse responses of price to income in the two cities are mainly attributed to the different market structures. While price anomalies are found occasionally, the housing prices are considered reasonable in Beijing and Shanghai for most of the time. Furthermore, the analysis on the role of macro-control policies in Chinese housing markets reveals that government interventions regulate the market ineffectively at the current stage.     

中国松香产品对外贸易特征与结构分析——基于2001~2011年数据

对2001²011年中国松香产品对外贸易特征及结构进行实证分析研究的结果表明:中国松香产品贸易以出口为主,进口量相对较小;近年来松香出口额增长迅猛,但进口额增长乏力;国际松香价格一路高涨,而中国松香产品出口价格远低于进口松香价格;松香进出口均主要集中于380610和380690两类松香,出口主要集中于欧盟、美国、日本和韩国,出口市场集中率较高。因此,提出主动实施松香深加工和品牌战略、控制松香出口规模、多元化出口市场战略、关注新兴市场等对策建议。