Pensions refer to payment made to a person (or their dependants) after retirement. Pension systems vary across countries and no single model fits all. Generally, there is a mix of public and private pension provision. Public pensions are statutory, most often financed on a pay-as-you-go basis (where current contributions pay for current benefits) and managed by public institutions. Private pensions are in some cases mandatory, but more often are voluntary, funded, employment-based pension plans or individual retirement savings plans. Pensions may also be supplemented by housing wealth, personal financial wealth, and publicly provided services.