Corporate credit unions are united on a cooperative basis in the Central Credit Union (US Central Credit Union). Most modern credit unions represent specialized consumer cooperatives of citizens associated by the principle of social community: place of work, place of residence, profession, or any other shared interest. The number of shareholders of a credit union is limited and formalized by a list. Limit of the number is defined by the assembly and such assembly establishes the charter. Among the U.S. credit unions, there are three groups that differ in terms of assets, shareholders, and business services. As of the January 1, 2012 the national associations and confederations unite more than 196 million members participating in the 51,013 credit unions in 100 countries. Until the mid-XX century, credit unions in the United States had little assets that did not exceed, as a rule, 100 thousand dollars Credit unions encourage the proper use of shareholders savings, developing social programs (education, health, recreation, housing, etc.). Unlike banks credit unions limit their activities to a closed circle of people.