Like the credit cooperatives, credit unions form associations of a higher level, which are called corporate credit unions. 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. Until the 70's there was a proliferation of the U.S. credit unions due to the increase of their number and the number of shareholders, although it must be acknowledged that there was also and a qualitative growth. Credit unions are competitors of savings institutions, adding interest on deposits of members. This applies to the shares, as well as to additional funds transferred to the account in the credit union. Taking a decision to join a credit union, citizens create an organization through which they participate in the shared savings by mutual crediting and joint (collective) use of personal savings. Credit unions encourage the proper use of shareholders savings, developing social programs (education, health, recreation, housing, etc.). Unlike banks, in order to use the services of a credit union, you have to become its member, having written an application and having paid thus shares and membership fee. Unlike banks credit unions limit their activities to a closed circle of people. A potential new member of a credit union must submit a recommendation of shareholders in which the referee becomes a warrant of a future member of the credit union.