Figure 3
Two line graphs depict CUSUM and CUSUM of squares test results over time. Panel A shows a line graph with the horizontal axis labeled with years ranging from 1990 to 2020 and the vertical axis ranging from -20 to 20. The blue line represents the CUSUM values, and the red dashed lines indicate the 5 percent significance levels. The CUSUM line fluctuates around the zero mark with some peaks and troughs but generally stays within the significance bounds. Panel B shows another line graph with the horizontal axis labeled with years ranging from 1990 to 2020 and the vertical axis ranging from -0.4 to 1.4. The blue line represents the CUSUM of squares values, and the red dashed lines indicate the 5 percent significance levels. The CUSUM of squares line shows an upward trend, starting below zero and gradually increasing, staying within the significance bounds.CUSUM and CUSUM of square test results