Comparative Study Of Some Time Series Models On The Monthly Consumer Price Index (Cpi) Of Consumer Goods In Nigeria
Edike Nnamdi
Department of Mathematics, Ambrose Alli University, Ekpoma, Nigeria
Braimah Joseph Odunayo
Department of Mathematics, Ambrose Alli University, Ekpoma, Nigeria
Ismaila Olawale Adegbite
Department of Statistics, Osun State Polytechnic, Iree, Nigeria
Adedotun Olurin Omisore
Department of Statistics, Osun State Polytechnic, Iree, Nigeria
Abstract
The Consumer Price Index (CPI) measures the average change over time in prices of goods and services consumed by the people for day-to-day living. It measures the inflation rate in the nation’s economy. This study is a comparative study of some time series models using the monthly Consumer Price Index (CPI) of consumer goods in Nigeria. The data used for the study is the monthly CPI of all items from January 2009 to January 2021, sourced from the National Bureau of Statistics (NBS). The CPI was computed using November 2009 as the base period. The study seeks to obtain the time series model that best fits the data to make more accurate forecasts from the series. Of the four models considered in the study, the double exponential smoothing model wasfound to be the best model for the monthly CPI and was therefore employed to make a 18-month forecast of the series. The study equally reveals a steady rise in the CPI from January 2009 to May 2016. A steeper upward trend was observed from May 2016 onward. The Mean Square Deviation (MSD), Mean Absolute Deviation (MAD), and the Mean Absolute Percentage Error (MAPE) were used to estimate the accuracy of the fitted trend values and forecasts