The rise of Robber Barons and their monopoly trusts in the late nineteenth and early twentieth centuries underscores that, as we already emphasized in chapter 3, the presence of markets is not by itself a guarantee of inclusive institutions. Markets can be dominated by a few firms, charging exorbitant prices and blocking the entry of more efficient rivals and new technologies. Markets, left to their own devices, can cease to be inclusive, becoming increasingly dominated by the economically and politically powerful. Inclusive economic institutions require not just markets, but inclusive markets that create a level playing field and economic opportunities for the majority of the people. Widespread monopoly, backed by the political power of the elite, contradicts this. But the reaction to the monopoly trusts also illustrates that when political institutions are inclusive, they create a countervailing force against movements away from inclusive markets. This is the virtuous circle in action. Inclusive economic institutions provide foundations upon which inclusive political institutions can flourish, while inclusive political institutions restrict deviations away from inclusive economic institutions. Trust busting in the United States, in contrast to what we have seen in Mexico illustrates this facet of the virtuous circle. While there is no political body in Mexico restricting Carlos Slim's monopoly, the Sherman and Clayton Acts have been used repeatedly in the United States over the past century to restrict trusts, monopolies, and cartels, and to ensure that markets remain inclusive.