Even though more than 2.3 percent of people have IQs below the 70 cutoff, only about 1 percent of the population has an intellectual disability. The prevalence of intellectual disability is lower than the prevalence of low IQs because

The prevalence of intellectual disability is lower than the prevalence of low IQs because:

1. Many people with intellectual disabilities die at a younger age. As an indication of these facts, studies show that twice as many school-age children as preschoolers have intellectual disabilities, but the prevalence rates drop again among adults (Grossman, 1983).

2. IQs cannot be adequately assessed among very young children, who therefore may be omitted from prevalence figures.

3. many adults with low IQs are not considered to have intellectual disabilities because they have adaptive skills.

for many centuries there were important factors which the economies of the muslim empires developed increasingly. they applied economic procedures in production, investment, finance, taxation and property. they used to tax certain goods (for example: harvest), they charged interest on money lent, they signed contracts with merchants; they relied on a common currency, and they used checks as well as promissory notes. with the money collected by means of taxation, the government provided the needy with an income. in addition, trading networks covered huge distances, so far regions started to have contact and exchange goods. this trade network covered areas of asia, africa and europe.