In the U.S., credit unions have a clear organizational structure. All credit unions belong to one or the other parent credit union (there are 35 of them in the U.S.). Specialization of credit unions to provide financial services to its shareholders requires a particularly strict regulation of membership and acceptable activities. Typically new members of the credit union become citizens having suretyship or recommendations from their friends - members of the credit union. Historically, credit unions have grown from the experience of credit cooperatives, but they took the experience of organizations of mutual aid of citizens by moving methods of social self-protection from labor and toward consumption. Credit union as a consumer cooperative operates on the principles of equality of all its members.