Figure 4.
The four panels are labelled nationwide, eastern region, central region, and western region. Each panel displays horizontally aligned kernel density curves for years twenty eleven through twenty twenty one, with year labels listed along the left of each panel. The horizontal axes show numeric scales ranging approximately from minus zero point zero five to zero point two five in panels a, b, and c, and from zero to zero point two zero in panel d. Each year is represented by a single smooth density curve positioned on its own horizontal baseline. Curves overlap vertically across years within each panel.The results of kernel density estimation
Source: Authors’ own work