Prevalence data on speech sound disorders are problematic for a number of reasons:
- Definitions of the disorder are inconsistent.
- Various studies have relied on teacher, parent, and/or speech-language pathologist (SLP) reports in varying combinations.
- Most of the prevalence research that has been published has come from the United Kingdom, Australia, and Canada and often focuses on specialized populations in those countries or in the United States; thus, it can be difficult to determine the extent to which those data can be generalized to the United States population overall.
The most widely cited summary of speech sound disorder prevalence is a systematic review conducted by Law, Boyle, Harris, Harkness, & Nye (2000). They reported prevalence estimates ranging from 2% to 25% of children ages 5 to 7 years.
The limited epidemiologic data that are available suggest that prevalence is slightly higher in boys than girls, and has a low positive correlation with socioeconomic status.