the term 30-million-word gap (often shortened to just the word gap) was originally coined by betty hart and todd r. risley in their book "meaningful differences in the everyday experience of young american children", and subsequently reprinted in the article "the early catastrophe: the 30 million word gap by age 3". in their study of 42 midwestern families, hart and risley physically recorded an hour's worth of language in each home once a month over 2½ years. families were classified by socioeconomic status (ses) into "high" (professional), "middle/low" (working class) and "welfare" ses. they found that the average child in a professional family hears 2,153 words per waking hour, the average child in a working-class family hears 1,251 words per hour, and an average child in a welfare family only 616 words per hour. extrapolating, they stated that, "in four years, an average child in a professional family would accumulate experience with almost 45 million words, an average child in a working-class family 26 million words, and an average child in a welfare family 13 million words."