Myopia

"The global prevalence of refractive errors has been estimated from 800 million to 2.3 billion.[20] The incidence of myopia within sampled population often varies with age, country, sex, race, ethnicity, occupation, environment, and other factors.Variability in testing and data collection methods makes comparisons of prevalence and progression difficult.
In some areas, such as Japan, Singapore and Taiwan, up to 44% of the adult population is myopic.
A recent study involving first-year undergraduate students in the United Kingdom found that 50% of British whites and 53.4% of British Asians were myopic.
In Australia, the overall prevalence of myopia (worse than −0.50 diopters) has been estimated to be 77%.In one recent study, less than 1 in 10 (8.4%) Australian children between the ages of 4 and 12 were found to have myopia greater than −0.50 diopters. A recent review found that 16.4% of Australians aged 40 or over have at least −1.00 diopters of myopia and 2.5% have at least −5.00 diopters.
In Brazil , a 2005 study estimated that 6.4% of Brazilians between the ages of 12 and 59 had −1.00 diopter or myopia or more, compared with 2.7% of the indigenous people in northwestern Brazil.Another found nearly 1 in 8 (13.3%) of the students in one city were myopic.
In Greece, the prevalence of myopia among 15 to 18 year old students was found to be 36.8%.
In India, the prevalence of myopia in the general population has been reported to be only 6.9%.
A recent review found that 26.6% of Western Europeans aged 40 or over have at least −1.00 diopters of myopia and 4.6% have at least −5.00 diopters.
In the United States, the prevalence of myopia has been estimated at 20%.Nearly 1 in 10 (9.2%) American children between the ages of 5 and 17 have myopia. Approximately 25% of Americans between the ages of 12 and 54 have the condition. A recent review found that 25.4% of Americans aged 40 or over have at least −1.00 diopters of myopia and 4.5% have at least −5.00 diopters.
A study of Jordanian adults aged 17 to 40 found that over half (53.7%) were myopic."