国内外玉米价格传导关系影响研究基于收购政策市场化改革背景

[目的]玉米在国家粮食安全中占有重要地位,是国内外市场联系最为紧密的大宗农产品之一。文章旨在探讨收购政策市场化改革前后,国内外玉米价格传导关系是否发生变化,为政府推进玉米供给侧改革提供理论依据。[方法]该文选取2009—2018年国内外玉米价格周度数据,利用向量误差修正模型和门限向量误差修正模型分别对收购政策市场化改革前后国内外玉米市场间价格传导关系进行实证分析。[结果]长期内,国内外玉米价格存在长期稳定的均衡关系,国际玉米价格对国内玉米价格具有持续稳定的正向传导关系;短期内,收购政策市场化改革前,国内外玉米价格间存在线性调整关系,具体表现为国际玉米价格向国内玉米价格单向传导关系;而收购政策市场化改革后,国内外玉米价格短期非均衡误差调整动态存在门限非对称调整关系,且改革后未来国内玉米价格受到当期国内玉米价格影响较大。[结论]这些结论对推进玉米供给侧改革,维护国内玉米市场的健康有序发展有一定的参考作用。     

Fighting global food price rises in the developing world: the response of China and its effect on domestic and world markets

This article addresses how China is being affected by and is responding to the world food crisis. So far, Chinese officials have responded to higher world prices by drawing down stocks and limiting exports of major grains. These policy instruments were not available for soybeans, so domestic prices of soy and other oilseeds have risen with international prices. Using a global CGE model, we show that the initial world price rise was largely due to higher world oil prices and demand for biofuels as opposed to other factors, especially in maize and soybeans. China's response to this shock has kept domestic grain prices low relative to world grain markets and to domestic soybean prices. As grain stocks are depleted, however, demand growth will push domestic prices back into alignment. Anticipating this pressure on consumers and accelerating supply response through public investment will facilitate adjustment.     

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.     

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.     

Evaluating price transmission between global agricultural markets and consumer food price indices in the European Union

This paper uses error correction models to evaluate the extent to and speed at which world agricultural commodity price movements affect consumer food prices in the European Union member states. We consider three types of world commodity price indices, each containing different commodities and weighting criteria. Results reveal a long‐run relationship between world agricultural commodity and consumer food prices in over half of the member states. Consumer prices in different member states and categories of member states respond differently to specific world price indices, suggesting that there are disparities in the structure and the efficiency of their food markets. The eurozone founders generally have lower transmission elasticities. This should be taken into account when predicting the impacts of extreme world price volatility and consumer food price rises, prompting governments to pay attention to the most vulnerable households.     

The effects of NCPB marketing policies on maize market prices in Kenya

The Government of Kenya pursues maize marketing policy objectives through the National Cereals and Produce Board (NCPB), which procures and sells maize at administratively determined prices, and stores maize as a contingency against future shortages. A private sector marketing channel competes with the NCPB. This article estimates the effects of NCPB activities on the historical path of private sector prices in Kenyan maize markets between 1989 and 2004. The analysis is carried out using a reduced form vector autoregression model (VAR) estimated with sparse data and imposing only minimal identification restrictions. Results show that NCPB activities have stabilized maize market prices in Kenya, reduced price levels in the early 1990s, and raised average price levels by roughly 20% between 1995 and 2004. Over the past decade, the price-raising activities of the NCPB have transferred income from urban consumers and a majority of small-scale farm households that are net buyers of maize to a relatively small number of large- and small-scale farmers who are sellers of maize.     

Cross country maize market linkages in Africa: integration and price transmission across local and global markets

In order to study short‐run price shock propagation, we model twenty seven Sub‐Saharan Africa (SSA) domestic maize markets within a Global Vector Autoregression framework. The main purpose is to fully embed multilateral trade flows as a way to better structure local price transmission dynamics and interdependencies, and get a more comprehensive picture of food price shocks propagation. We found significant between‐country market contagion and prompt regional price shock propagation when trade connection exists. Yet, the integration of SSA domestic maize markets within the continent and with global markets remains generally weak. Furthermore, under regular market conditions, most local price series appear to be more responsive to regional neighbors than to global shocks.     

Applying cointegration and error correction to measure trade linkages: maize prices in the United States and Mexico

The impact of U.S.‐grown maize on Mexican markets is a subject of heated debate, and is complicated by limited substitution between white and yellow maize as well as regional price differences within Mexico. This article improves on previous analyses using a detailed data set of white maize prices reported weekly in 11 states across Mexico from 1998 through 2005. Using cointegration analysis and the error‐correction model, we find that prices between the United States and Mexico do not share a common long‐run relationship. Within Mexico, prices in Michoacán and Oaxaca are only weakly related with prices in neighboring states, whereas prices in Sinaloa and Jalisco exert considerable influence on prices elsewhere in Mexico. We conclude that, despite North American Free Trade Agreement (NAFTA), white maize prices in Mexico are determined by local conditions including particularly the degree of integration to other regions within Mexico.     

Decomposing changes in agricultural price gaps: an application to Russia

The article develops a method for decomposing changes in agricultural price gaps, defined as the difference between a commodity's domestic producer and border prices. We use OECD's procedure for decomposing changes in the market price support part of producer support estimates as the starting point for our decomposition method, and our method provides a basis for critiquing OECD's decomposition approach. The transmission of changes in border prices (world prices and the exchange rate) to domestic prices is a key element in the decomposition. The method is demonstrated using Russian agricultural price gaps. The results support the argument that for Russian agriculture during the transition period, the main cause of changes in price gaps has been incomplete transmission of changes in the exchange rate to domestic prices, and where the weak transmission results mainly not from policy intervention, but rather from deficient market conditions, in particular poor market infrastructure. The policy implication is that underdeveloped infrastructure has strongly limited the benefits to the Russian economy from agricultural trade liberalization.     

Price transmission,asymmetric adjustment and threshold effects in the cotton supply chain: a case study for Vidarbha,India

This study examines price transmission asymmetries in Vidarbha's (India) cotton supply chain from 2002 to 2012. The analysis takes account of thresholds in price adjustments toward their long‐run equilibrium. The first stage considers the price dynamics between international and Indian domestic cotton prices. The second stage considers price transmission from domestic to farm gate cotton prices in Vidarbha. Results from the first stage indicate that Indian and international cotton markets are well‐integrated. In contrast, the second stage reveals significant threshold‐type nonlinearities as well as asymmetries in price transmission between domestic and farm gate prices. The short‐run dynamics suggest that the pass‐through from domestic to farm gate prices is larger when domestic prices decrease than when they increase. Moreover, back of the envelope calculations suggest that the loss in revenue for a typical farmer from a decrease in domestic price is larger than the gains from an increase in domestic price of the same magnitude. The implication is that traders benefit from price fluctuations at the expense of farmers. Evidence from fieldwork in Vidarbha suggest that asymmetries revealed in this analysis may be linked to trader's market power and inadequate market information among farmers.     

Factors influencing the profitability of fertilizer use on maize in Zambia

Fertilizer use remains very low in most of Africa despite widespread agreement that much higher use rates are required for sustained agricultural productivity growth. This study uses longitudinal farm survey data to estimate maize yield response functions in a relatively high-potential zone of Zambia to determine the profitability of fertilizer use under a range of small-farm conditions found within this zone. The theoretical framework used in this study incorporates agronomic principles of the crop growth process. We generalize the asymmetric production models and define a concept of yield scaling factors. The model distinguishes different roles of inputs and non-input factors in crop production. We estimate the effects of conventional production inputs as well as of household characteristics and government programs on maize yield. The results indicate that recommended fertilizer application rates in the two specific years were often unprofitable, given observed price conditions and the yield response to fertilizer. However, there was substantial variability in yield response to fertilizer based upon the rate of application, the timeliness of fertilizer availability, the use of animal draught power during land preparation, and whether the household incurred the death of an adult member in the past three years. These modifying factors, as well as variations in input and output prices due to proximity to roads and markets, substantially affected the profitability of fertilizer use on maize.     

Determination of the international maize price: What is the growing role of Brazil and Ukraine?

This paper examines the relationships among maize prices for four countries to determine if newly emerging exporters, Brazil and Ukraine, influence the international price of maize. Our work focuses on each market's participation in the price discovery process rather than trying to determine a price leader. We find that the United States plays the largest role in price discovery, followed by Argentina, Brazil, and Ukraine. We also search for export thresholds and find that Ukraine's contribution to price discovery rises slightly when an export threshold of 2.3 million tons is reached. No export thresholds were found for Brazil. Export thresholds for Argentina were found but only have a minor impact on price relationships. We also found that price relationships vary considerably across seasons of the year.     

The effects of the Food Reserve Agency on maize market prices in Zambia

Over the last decade, governments throughout eastern and southern Africa have increasingly used strategic reserves and/or marketing boards to influence grain market outcomes, yet little is known about how these activities are affecting grain markets. This article estimates the effects of the Food Reserve Agency (FRA) on maize market prices in production and consumption regions in Zambia using a vector autoregression model and monthly data from July 1996 through December 2008. In recent years, FRA has become the dominant buyer of smallholder maize in Zambia. Simulations show that FRA activities stabilized market prices throughout the July 1996–December 2008 study period and raised mean prices between July 2003 and December 2008 by 17–19%. The price raising effects of FRA policies have assisted surplus maize producers but adversely affected net buyers of maize in Zambia, namely urban consumers and the majority of the rural poor. The increase in maize price stability is unlikely to have had substantial welfare effects on poor households. In contrast, relatively wealthy producers are likely to have benefited from the higher average and more stable maize prices resulting from FRA policies.     

Modeling price transmission between farm and retail prices: a soft switches approach

Vector error correction models (VECM) are used to model price transmission when farm and retail prices are cointegrated. To allow for nonlinearity in the cointegration process, researchers may specify thresholds to break the error correction process into regimes according to whether the retail price is above, below, or close to its equilibrium value given farm prices.  However, because the coefficients in a VECM can change when there is movement from one regime to another, the model can be discontinuous.  This implies sudden, “hard” regime changes. In this study, we extend the threshold VECM to include features of smooth transition autoregression (STAR) models. Our approach allows for gradual, soft regime changes.  An empirical application to retail cheese and farm milk prices is presented.     

Transaction Cost Thresholds in International Rice Markets

Recent episodes of high and volatile prices for grains such as rice have raised concerns about their implications for hunger and poverty. We model price relationships between international rice prices and 221 domestic prices in 47 developing countries that import rice. We use a threshold vector error correction model that accounts for transaction costs of trade in spatial price transmission, and an improved regularised Bayesian threshold estimator for threshold models. Our results show that threshold values are higher after 2008 than before, which suggests that transaction costs in international rice trade have increased in recent years. Threshold values are highest for Latin American countries followed by African and Asian countries, and higher for retail than for wholesale prices. Since 2008, price transmission is slower in countries that responded to high and volatile prices with domestic market‐based interventions such as price controls and faster in countries that responded by lowering tariffs and by implementing production support measures.     

Enhancing food security in South Sudan: the role of markets and regional trade

South Sudan faces serious problems of food insecurity due to low levels of domestic food production, periodic droughts, widespread poverty, and since late 2013, renewed armed conflict. This article explores market price behavior using cointegration analysis and estimates the effects of production and trade shocks through multimarket model simulations. We show that market prices in the capital city, Juba, of both maize and sorghum are cointegrated with import parity prices of these cereals sourced from Uganda, consistent with observed trade flows. Model simulations, using econometrically estimated demand parameters, suggest that private sector imports of maize and wheat would greatly mitigate the potential fall in consumption in the case of a decline in domestic cereal production. Other simulations indicate that if total imports of cereals are reduced by one‐third (still more than two times the levels of food aid in 2013) because of disruptions to private market flows, domestic prices of cereals could rise by 45% or more. The article concludes that whatever measures are taken involving national food security reserves, it is crucial that government policy serves to maintain incentives for private sector imports to avoid destabilizing market supplies, domestic prices, and ultimately, food consumption of the poor.     

Dynamics of rice prices and agricultural wages in the Philippines

Rice trade liberalization in the Philippines should decrease domestic rice prices impacting both agricultural wages and the welfare of agricultural wage earners. This study examines the short-run and long-run relationship between rice prices and agricultural wages in the Philippines using a neoclassical wage determination model. Three empirical frameworks are used—a cointegration/error correction framework, which assumes nonstationary variables in long-run equilibrium, a first difference model that assumes nonstationary variables but no long-run equilibrium, and an OLS framework that assumes the model variables are stationary. Conclusions are reasonably robust across the three empirical frameworks with wages adjusting positively to rice price changes with a short-run elasticity of 0.29 to 0.57, and a long-run elasticity of 0.70 to 1.0 in preferred models. An analysis of welfare implications suggests that although households that are heavily reliant on agricultural wages for income will be adversely affected by rice price decreases, other households will benefit.     

Agricultural price transmission across space and commodities during price bubbles

This article investigates agricultural price transmission during price bubbles. The empirical approach concerns the horizontal transmission of cereal prices both across different market places and across different commodities. The trade policy intervention put forward to mitigate the impact of price exuberance is considered. The analysis is performed using Italian and international weekly spot (cash) price data over years 2006–2010, a period of generalized turbulence of agricultural markets. Firstly, the properties of price time series are explored; then, interdependence across prices is specified and estimated by adopting appropriate cointegration techniques. Results suggest that the bubble had only a slight impact on the price spread and the temporary trade‐policy measure, when effective, has limited this impact.     

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.     

High food commodity prices: will they stay? who will pay?

Much of the public discussion of the food price crisis has focused on the sharply increased use of food commodities for biofuel production, framing debate in simple food versus fuel terms. Reality is more complex. Multiple forces drove food prices to high levels and, according to findings we report in this article, these forces will sustain high prices over the medium term. We also find that the distinction between high world prices for food commodities and the consumer costs of food is an important one to make. Food consumers do not buy raw food commodities at international prices. The degree to which the price of traded food commodities and the price of food are related depends on a long list of factors, most of which operate to dampen price transmission. In the search for appropriate policy response, it is essential to measure consumer effects correctly and to apportion properly the causes of current high prices.