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Many individuals with poor reading comprehension have levels of reading comprehension that are consistent with deficits in their ability to decode the words on the page. However, there are individuals who are poor at reading comprehension despite being adequate at decoding. This phenomenon is referred to as specific reading comprehension deficit (SRCD). The two purposes of this study were to use a new approach to estimate the prevalence of SRCD and to examine the extent to which SRCD can be explained by the simple view of reading. We used model-based meta-analysis of correlation matrices from standardized tests to create composite correlation matrices for the constructs of reading comprehension, decoding, and listening comprehension. Using simulated datasets generated from the composite correlation matrices, we used residuals from regressing reading comprehension on decoding to create a continuous index of SRCD. The prevalence of SRCD is best represented not as a single number but as a continuous distribution in which prevalence varies as a function of the magnitude of the severity of the deficit in reading comprehension relative to the level of decoding. Examining the joint distribution of the residuals with reading comprehension makes clear that the phenomenon of reading comprehension that is poor relative to decoding occurs throughout the distribution of reading comprehension skill. Although the simple view of reading predictors of listening comprehension and decoding makes significant contributions to predicting reading comprehension, nearly half of the variance is unaccounted for.

How prevalent is dyslexia? A definitive answer to this question has been elusive because of the continuous distribution of reading performance and predictors of dyslexia and because of the heterogeneous nature of samples of poor readers. Samples of poor readers are a mixture of individuals whose reading is consistent with or expected based on their performance in other academic areas and in language, and individuals with dyslexia whose reading is not consistent with or expected based on their other performances. In the present article, we replicate and extend a new approach for determining the prevalence of dyslexia. Using model-based meta-analysis and simulation, three main results were found. First, the prevalence of dyslexia is better represented as a distribution that varies as a function of severity as opposed to any single-point estimate. Second, samples of poor readers will contain more expected poor readers than unexpected or dyslexic readers. Third, individuals with dyslexia can be found across the reading spectrum as opposed to only at the lower tail of reading performance. These results have implications for screening and identification, and for recruiting participants for scientific studies of dyslexia.