American Sign Language (ASL) is the natural signed language used in the United States and the majority of Canada. Estimating the numbers of users of ASL is complicated by several factors. According to the National Institute on Deafness and Other Communicative Disorders, approximately 2 or 3 of every 1,000 children born in the United States have detectable hearing loss in one or both ears. More than 90% of deaf children are born to hearing parents and thus do not learn ASL natively in the home; most deaf children learn ASL in the school environment. Most of these students will, as adults, regard ASL as their preferred language.

A 1972 survey of the deaf population of the United States estimated that approximately 500,000 people, regardless of hearing ...