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. 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. Over 30% of the assets of credit unions are investments in government securities, certificates of deposit of banks and savings loan associations, as well as in the parent credit unions, and other risk-free investments. In the case of default the shareholder - individual will respond with its property and, in addition, is jointly and severally liable with the credit union's commitments. In the UK, credit unions are a source of financing of people groups. This tool is not widely used. Credit unions, like today's credit unions, emerged in the 19th century in Germany as a result of crop failure and famine.