SLI, or specific language impairment, is a common speech and language disorder. Several studies have found that between 3-7% of kindergarten aged children have a diagnosis of SLI. Longitudinal studies show that language delays in early childhood often persist into the school-aged years without treatment. The prevalence and prognosis of SLI has been well-documented in multiple epidemiological studies published between 1978-2012.

1. How common is SLI?
References
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McLeod, S., & Harrison, L. J. (2009).Epidemiology of speech and language
impairment in a nationally representative sample of 4-to 5-year-old
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Silva, P. (1980). The prevalence, stability and significance of developmental
language delay in preschool children. Developmental Medicine and Child
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Stevenson, J., & Richman, N. (1978).The prevalence of language delay in a
population of three year old children and its association with general
retardation.Developmental Medicine and Child Neurology, 18, 431-441.
Tomblin, J. B., Records, N. L., Buckwalter, P., Zhang, X., Smith, E., & O'Brien, M.
(1997).Prevalence of specific language impairment in kindergarten
children.Journal of Speech and Hearing Research, 40(6), 1245-1260.
Weindrich, D., Jennen-Steinmetz, C., Laucht, M., Esser, G., & Schmidt, M. H.
(2000).Epidemiology and prognosis of specific disorders of language and
scholastic skills.European Child and Adolescent Psychiatry, 9(3), 186-194.
Dorothy Bishop, November 2012
References to accompany RALLI presentation