PREVALENCE OF LEARNING DISABILITYThe”real” prevalence of LD is subject to much dispute because of the lack off anagreed-upon definition of LD and objective diagnostic criteria. Some haveargued that the currently recognized 5% prevalence rate is excessive and isbased on vague definitions, leading to inaccurate identification Lyon, 1996.On the other hand, research efforts to identify objective early indicators ofLD in basic reading skills have concluded that virtually all children scoringbelow the 25th percentile on standardized reading test can meet the criteriafor having a reading disorder. While less is known about LD in writtenexpression, researchers 8% and 15% of the school population. Research alsoindicates that approximately 6% of the school population has difficulties inmathematics which cannot be attributed to low intelligence, sensory deficits oreconomic deprivation (Reid Lyon.
G. Learning Disabilities, Jr. The Future ofchildren, Special Education for Students with Disabilities Vol.6.No.1 – Spring1996 p.p.
57).Therehave been a number of estimates of prevalence of LD in the world. Emerson,Hatton, Felce and Murphy (2001) suggested that prevalent mild learningdisability is between 2.5 percent and 3 percent.
The World Health Organization(1985) also put the figure of mild LD for children in industrialized countriesat 2 percent – 3 percent. Smith, et al, (2001) reports that in 1995-1996 schoolyear, 51.2 percent of school going children were learning disabled in UnitedStates which implied that there were more students with LD than any otherdisability. It has generally been approximated that 4 boys are identified toevery girl (4:1), meaning that there are more boys with LD than girls. InNetherlands, approximately 57,700 of them have a severe handicap (Ministry ofEconomic Affairs 2000).
Owing to lack of accurate data, prevalence of LD inCanada, United Kingdom (UK), China, Japan, India, Australia, South Africa,Kenya, Tanzania and Uganda has been extrapolated to be 1.69% of the totalpopulation of respective countries. The statistics used for the prevalence ofLD are typically based on US, UK, Canadian or Australian statistics.Theseestimates cannot be accepted uncritically. However, Lyon suggests that itshould be made clear that difficulties in the identification of children withlearning disabilities do not make the disabilities any less “real” to thestudent who cannot learn to read, write, or understand mathematics despite goodintelligence, an adequate opportunity to learn, and ostensibly good teaching.
The question remains, however, of how to go about increasing the ability toidentify individuals with LD accurately. Valid prevalence estimates depend upona set of criteria for identification that are clear, observable, measurable,and agreed upon.