Black beans and soybeans are important agribusiness activities in the Rio Grande do Sul, but they present distinct features at the production and at the marketing levels. The aim of this article is to evaluate the production value (PV) growth of these activities through its decomposition into three main components: area, productivity and price. The study also aims to determine how shocks in these variables are transmitted from one agricultural season to another in the PV. The data used comprised the period of 1977 to 2010 and the shift share's model was used to decompose the share of each component on the VP growth. Additionally, it was used a series of vector auto regression models to determine the current and lagged effects of these components over PV. The results show that in the short run the component productivity is the main responsible for variation in the PV. However, in the long run the decrease in the real prices is the most important determinant of the PV reduction. Positive shocks on the three components yields immediately positive reaction on PV. The propagation of the effects resembles the cobweb model with more dynamics adjustments for soybean than for black beans
shifts on production value; soybean; bean; VAR; Rio Grande do Sul
