Like the credit cooperatives, credit unions form associations of a higher level, which are called corporate credit unions. 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. To increase the number of credit unions in 1979 was adopted the corresponding law that serves as the legal basis of their activity. Unlike banks credit unions limit their activities to a closed circle of people.