Data cover both social security reserve funds and sovereign pension reserve funds, the two main categories of public pension reserve funds. Social security reserve funds are set up as part of the overall social security system. They are funded chiefly by surpluses from employee and/or employer contributions over current payouts and, in some cases, by top-up contributions from the government through fiscal transfers and other sources. They may be managed either as part of a national social security scheme or by an independent - often public sector - fund management entity. Sovereign pension reserve funds are funds established by governments (independently of social security systems), who finance them directly through fiscal transfers. They are usually mandated to finance public pension expenditures at a specific future date. Some are not allowed to make any payouts for decades.