(iii) Density and rate of decline vary with the region of the United States. The contrast between the Northeast (Figure 4.3A), the South (Figure 4.3B), and the West (Figure 4.3c) comes out very strongly: the Northeast with its high overall density and steep lapse rate, the South with its lower density and irregular lapse rate, and the West with its precipitous lapse rate, stand in marked regional contrast.