The rate of incidence of thyroid disorders depends on the particular disorder. For example, as many as 50 percent of people may have thyroid nodules, but in most cases these do not cause problems. Some congenital thyroid disorders occur in less than one tenth of a percent of the population. When it comes to thyroid cancer, some cancers of the thyroid are much more common than others. Generally, thyroid disorders tend to affect older people more than younger people.