Measuring market integration for apples on the South African fresh produce market: a threshold error correction model

Apples constitute the bulk of deciduous fruit produced in South Africa, i.e. in 2000, apples made up the largest percentage of the deciduous fruit crop (43%). From 991/92 to 2002/03 production averaged 574 850 tons per annum with a standard deviation of 43 922 tons. The average distribution of the apple crop between the local market, exports and processing is more or less even. Because of its potential lucrative nature much emphasis in the apple industry is afforded to exports, but relatively little is known about how price transmission takes place on the domestic fresh produce markets (FPMs). Moreover, it is increasingly recognized that the formulation of market-enhancing policies to increase the performance of the local market requires a better understanding of how the market functions. Aggregate market performance is better understood by studying the level of market integration that exists, which in turn is affected by transaction costs in the value chain. Hence, the primary objective of this study was to measure market integration for apples on the South African FPMs to determine the existence of long-run price relationships and spatial market linkages. Specific issues addressed in this study include, (i) determination of the effect of deregulation of the marketing of agricultural products in 1997 on average real market prices, price spread and volatility (risk), (ii) determination of how FPMs where apples are sold are linked and how prices are transmitted across these markets, (iii) determination of the threshold prices beyond which markets adjust and return to equilibrium, and (iv) establish the response of the FPMs to price shocks and how long it takes for shocks to be eliminated. The FPMs included in this study are Johannesburg, Cape Town, Tswhane, Bloemfontein, Port Elizabeth, Durban, Kimberley and Pietermaritzburg. The criteria for selecting the FPMs were based on net market positions (surplus or deficit area), geographical distribution, the volume of trade and the importance of the market to the national apple trade flow. The investigation revealed a statistically significant decline in real prices in six of the eight markets investigated, a statistically significant relation in prices (price spread) between the Johannesburg FPM and five other FPMs, as well as that the price spreads between these markets declined after deregulation, and that the variation in real apple prices declined for five of the eight markets after deregulation. Standard autoregressive (AR) and threshold autoregressive (TAR) error correction models were compared to determine whether transaction cost has significant effects in measuring market integration. Larger adjustment coefficients were found in the TAR model. This is an indication that price adjustments are faster in threshold autoregressive TAR models than in AR models. Also half-life deviations in the TAR model are much smaller than in the AR model. The TAR model requires less time for one-half of the deviation from equilibrium to be eliminated than the standard AR model. Therefore, it is better to use TAR models than AR models because TAR models give a more reliable result. In addition, the parameter estimates of the threshold vector error correction model were analyzed. The results show that bidirectional and unidirectional causality exist between Johannesburg FPM prices and other markets. Regime switching estimates to investigate market integration in the selected markets show that no persistent deviation from equilibrium existed for all but one market pair and no clear evidence was found to support improved market integration after market deregulation in 1997. A nonlinear impulse response function to investigate the impact of positive and negative price shocks in the Johannesburg FPM on other FPMs revealed that it takes about six to twelve months for positive and negative shocks to be completely eliminated in all the markets. Generally, the results obtained confirmed strong market integration in terms of apples for selected FPMs.