Sazonalidade em índices de preços : o caso do IPC-FIPE

Abstract

This article exams the issue of seasonal adjustment of price indices. This subject has been discussed frequently but consensus has yet to be reached. The case studied here is the Consumer Price Index elaborated by Pipe (CPI-Fipe), commonly used for indexation. The period analysed is Jan/80 to Dec/94. Using two alternative methodologies X-ll procedure and Structural Models for Time Series eleven seasonal items were identified. When the seasonal effects are considered together, it is observed that they cancel each other out. Thus, no seasonal pattern is transfered to the general index. Due to this result, seasonal adjustment of the CPI-Fipe is unnecessary.