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Prevalence of Dyslexia in The Netherlands

Leo Blomert and Anton de Vries

University of Maastricht, The Netherlands L.blomert@psychology.unimaas.nl

Abstract

Estimations of the prevalence of dyslexia vary between 2 and 10 % of the population. This variance is a consequence of criteria, sample size and the fact that the criteria are seldom independently validated. We therefore choose to take teacher judgments as criterion, to validate this criterion by an independent measurement of academic skills and to include a sample representative of the population. The teachers of grade 6 in 80% of all Dutch schools were asked to identify every pupil with reading and spelling problems and indicate the causes and severity of these problems. All Dutch children participate in a National Test of Schooling Abilities at the end of primary education. The survey results were validated with the National Test results. The results revealed a dyslexia prevalence of 3.6%. Teacher judgments accurately identified the pupils with dyslexia. As a group they were clearly separable form a general learning disabled group with equally severe reading and writing problems, a probable source of bias in previous estimates of dyslexia prevalence. Dyslexia is identifiable as a specific reading and spelling problem. This prevalence estimation is unique worldwide, as it is based on a national population and is validated by a uniform national measurement of academic abilities in all participants.

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