Tendência, quebra estrutural e persistência dos choques no prego da soja de 1960 a 2014

This paper aims at analyzing the following dynamic characteristics of real soybean prices: long-term trend, structural breaks and degree of persistence of shocks. As regards the trend, several studies have tested, in an aggregate or disaggregate way, the Prebisch-Singer hypothesis (PSFI) of deterioration of commodity prices in relation to those of manufactured goods. From the perspective of commodity-exporting countries, this exercise becomes relevant, given its impact on the terms of trade and domestic income. From Brazil's point of view, it is important to study the real price of its main export product, for analyzing the terms of trade in an aggregate fashion can result in a considerable aggregation bias. Therefore, once the soybean complex - which includes, in addition to the grain, bran and soybean oil - is the main group of products of Brazil's exports, it is appropriate to study whether there is a trend, structural breaks and persistence of shocks in the real price of soybeans. The methodology used involves the univariate time series analysisEvidence points to a high persistence of shocks in the real price of soybeans in the period 1960-2014, with a major structural break in 1973. Estimates indicate that the data generating process is stationary in difference, with significant drift and sign according to the PSFI.