Stylized Facts

about former Yugoslav republics economies

Industrial production
Industrial production Real Sector

Industrial production: Comparison of seasonal patterns

In this post a comparison between seasonal patterns of industrial production indices for six countries of the former Yugoslavia is given.

As discussed before there are a few time series graphs we can use to identify underlying seasonal pattern. These are seasonal and seasonal subseries plots, with some variations in their appearance. All these various plots will be used to illustrate differences or similarities in seasonal patterns of industrial production indices for these countries.

A seasonal plot is similar to a time plot except that the data are plotted against the individual “seasons” in which the data were observed. A seasonal plot allows the underlying seasonal pattern to be seen more clearly and to identify years in which the pattern changes. Because of the trends in each industrial production indices series (except in case of Croatia and Montenegro) all the monthly industrial production indices series were detrended.

Figure 1. Industrial production: Seasonal plots

From the seasonal boxplot we can identify quarters with highest volatility in industrial production indices. Both seasonal plots and seasonal boxplots show that industrial production indices of Bosnia and Herzegovina and Slovenia are least volatile. The most volatile industrial production indices time series are for Croatia and Montenegro.

Figure 2. Industrial production: Seasonal boxplots

Comparing how the median value on the seasonal boxplots are changing from quarter to quarter we can identify two groups of countries. The first include Bosnia and Herzegovina, Macedonia, Serbia and to some extent Croatia where the highest industrial production indices are achieved in the last few months (fourth quarter). The second group consists of Slovenia and Montenegro with the highest industrial production indices recorded in the March.

A seasonal subseries plot is another graphical tool for detecting seasonality in a time series. This plot allows you to detect both between groups and within group patterns (e.g., do January and June exhibit similar patterns), nature and changes of seasonality within particular season. The horizontal lines on this plot indicate the means for each quarter.

Figure 3. Industrial production: Seasonal subseries

Most of the seasonal subseries plots show variation around some constant level for respective months. In simple terms it means there is no tendency of increasing/decreasing industrial production indices in a particular month in the observed period.

Seasonal distribution plot is an alternative plot to seasonal boxplot. It also shows level of variation in seasonal component by month.

Figure 4. Industrial production: Seasonal distributions
(medians and confidence intervals)

Finally, seasonal density plot gives similar information as seasonal distribution plot. It shows the median value and the density around it using different shades of blue colour.

Figure 5. Industrial production: Seasonal density

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Zlatko Kovacic
Director of Wellington based My Statistical Consultant Ltd company. Retired Associate Professor in Statistics. Has a PhD in Statistics and over 35 years experience as a university professor, international researcher and government consultant.