Suppose the region has a total of 10 million workers. In Figure 4-3, points s, m, and b show one possible equilibrium. The utility level, u* is the same in all three cities, and the city workforce (1 million in the small city, 3 million in the medium-size city, and 6 million in the big city) add up to the regional workforce (10 million). As we saw earlier in the chapter, this is stable equilibrium because each city is on the negatively sloped portion of its utility curve.