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Estimates of worldwide and country-wide numbers of individuals with disabilities are problematic. The varying approaches taken to defining disability notwithstanding, demographers agree that the world population of individuals with disabilities is very large. For example, in 2004, the World Health Organization estimated a world population of 6.5 billion people, of those nearly two million were estimated to be moderately or severely disabled. [13] In the United States, Americans with disabilities constitute the third-largest minority [[after persons of Hispanic origin and African Americans); all three of those minority groups number in the 30-some millions in America. [13] According to the U.S. Bureau of the Census, as of 2004, there were some 32 million disabled adults [[aged 18 or over) in the United States, plus another 5 million children and youth [[under age 18). If one were to add impairments -- or limitations that fall short of being disabilities -- Census estimates put the figure at 51 million. [14]

There is also widespread agreement among experts in the field that disability is more common in developing than in developed nations