The grouping of the regions into four large areas with distinct characteristics (Southern, Western and Northern and Eastern) is explained in Annex 5. The regions were further divided into sub-groups according to type of work identified in the NSSO surveys. For example, the rural sub-population was split into self-employed and non-self-employed workers, as the self-employed group seems to have substantially different determinants of participation in the regressions (see Annex 5) and in the statistical analysis (see Figure 4 above) than the other occupations.