Membership in the credit union is voluntary and is open to all citizens bound by with joint work or residence, who wished to create a credit union to use its services and are willing to take on relevant commitments and responsibilities. Typically, donor contributions to the credit unions are targeted and used in the same statutory requirements and restrictions as the Mutual Financial Aid fund as a whole. Like the credit cooperatives, credit unions form associations of a higher level, which are called corporate credit unions. When organizing the credit union it is important that people know each other and know the extent to which each of them is trustworthy. 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. The main activities of credit unions, aimed at the organization of mutual aid and social support of citizens is not intended to profit.