As of 2011, ~235 million people worldwide were affected by asthma, and approximately 250,000 people die per year from the disease. Low and middle income countries make up more than 80% of the mortality. Rates vary between countries with prevalences between 1 and 18%. It is more common in developed than developing countries. One thus sees lower rates in Asia, Eastern Europe and Africa. Within developed countries it is more common among those who are economically disadvantaged while in contrast in developing countries it is more common amongst the affluent. The reason for these differences is not well known.