Tractors in Spain — A Dynamic Reanalysis

This paper presents a class of models obtained from the logistic curve to forecast stocks of goods. The dynamic approach allows variation of the parameters with time, thus allowing the model to adapt for changes. The observations are kept at the original scale and the model is reformulated in terms of the parameters. On-line estimates, forecasts and measures of performance are obtained. The methodology is applied to the stock of tractors in Spain. Fitted figures are obtained and compared with those from previous work.