As shown in Figure 4-4, local employment amplifies differences in population. Total employment increases by half in the small city (1 to 1.5 million), while it doubles in the medium-sized city (from 3 to 6 million) and triples in the large city (from 6 to 18 million). After incorporating local employment, the largest city has 12 times the total employment of the small city, up from six times before considering local employment. This occurs because the large city has a larger consumer base and can support a wider variety of products.