Like the credit cooperatives, credit unions form associations of a higher level, which are called corporate credit unions. Credit unions also differ from the traditional consumer cooperatives. Credit union services are available only to its shareholders. Share contributions are transferred to the credit union on the basis of membership for the whole stay of a shareholder as member of the credit union and are the basis of membership. 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. National Credit Union Insurance Fund was created by Congress in 1970 to insure deposits of credit union members in the amount of 100 thousand dollars. Income derived from the provision of services to its members, does not become the profit of credit union and is distributed among its members in proportion to their savings. 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.