Figure 9
The line graph plots data from 1990 to 2020 along the horizontal axis, labeled “year,” ranging from 1990 to 2020 with an interval of 10 years. The vertical axis ranges from negative 2 to 2 with an interval of 1. A thin brown line shows data values, which fluctuate narrowly around zero across the entire period. A shaded gray rectangle covers the area between negative 1.3 and 1.3 on the vertical axis, spanning all years horizontally. The data line remains within this shaded region at all times, with small oscillations but no major deviations. The background outside the shaded region is white. Note: All the numerical data values are approximated.Cumulative sum test using OLS CUSUM plot for parameter stability. Source(s): Authors’ computation