The nature of behavior analysis of monthly time series of different Sadri rice wholesale price

Evaluating the nature of behavior of time series for agricultural product prices plays an important role in improving policy making processes for managing and regulating food markets. Rice is one of the basic and most important foods in the food basket of Iranian households. In this research, the behavioral nature of the monthly time series of wholesale prices of common and top-notch Sadri rice during 1997-2016 (216 observations) was analyzed. To evaluate the statistical characteristics, trend modeling, principal component analysis, patterning the nature of behavior and recognition of seasonal and non-seasonal unit roots of these two time series were investigated. The results showed that the growth of wholesale prices of common and top-notch Sadri rice has been steadily increasing during the recent years (after 2007). Exponential function and the S-curve forms provided a better model for the time series procedures compared to the other forms. Holt-Winter multiple (HWM) algorithm was also the best nonparametric pattern for justifying the nature of behavior of the monthly time series of common and top-notch Sadri rice. Investigating the existence of seasonal unit roots revealed the similarity of the unit roots existence in the two studied time series. On the other hand, there was no long-term unit root in either of the two monthly time series of wholesale prices of common and top-notch Sadri rice at the 5% probability level.