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FIGURE 2-12A Ground transportation: horses to horsepower, 1900 and 1997.

SOURCE: S. Moore, J. L. Simon, and the CATO Institute. “The Greatest Century That Ever Was: 25 Miraculous Trends of the Past 100 Years.” Policy Analysis No. 364, December 15, 1999. Pp. 1-32.

FIGURE 2-12B Air travel, United States, 1928-2002.

SOURCE: US Census Bureau. “Statistical Abstract of the United States.” Available at:

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