There is a variety of financing arrangements through which individuals or groups of the population obtain healthcare. Government financing schemes, on a national or sub-national basis or for specific population groups, entitle individuals to healthcare based on residency and form the principal mechanism to cover healthcare costs in close to half of OECD countries. The other main method of financing is some form of compulsory health insurance (managed through public or private entities). Spending by households (out-of-pocket spending), both on a fully discretionary basis and part of some co-payment arrangement, can constitute a significant part of overall health spending. Finally, voluntary health insurance, in its various forms, can also play an important funding role in some countries.