they were partly obtained using an extremely low pure time preference rate of 0.1% in economic modeling. There is no consensus among economists and, according to the survey, no "one-size-fits-all" solution to the choice of social discount rate, owing to national variations. A regular reassessment and readjustment of the social discount rate used by each country is therefore required. Differences between private and social There are a number of qualitative differences between social and corporate discount rates and evaluation of projects associated with them. The governance of social project funding is different naturally, because estimating the benefits of social projects requires making ethically subtle choices about the benefits to others. For example, if it was presumed that a meteor will wipe out all life in a few years the SDR after the event is infinitely high. Alternately if we presume that the population will have many new and wonderful choices capturing benefits (i.e. they will be more wealthy) in the future that too raises the SDR of creating any given benefit. For example, choices about the SDR of environmental protection projects, such as funding the reduction of global warming, place a greater valuation on future generations. Contributors to social discount rate As with private discount rates, social discount rates can attempt to incorporate several factors (however, some factors may overlap or be inapplicable in a given analysis). One factor is a common expectation of increased wealth in the future, in which case a dollar received now, in the midst of relative poverty, has more utility than a dollar received later, in the midst of relative wealth. (This factor may not apply to non-monetary rewards, for example, measuring lives saved now versus lives saved later.) Similarly, economists refer to a "time value of money": a dollar received now might grant the recipient the option to either used the dollar now or to invest it (gaining interest) and using it next year, whereas a dollar received next year can only be used next year (and without the intervening interest). A third factor is that a proposed project may fail or become moot due to changing circumstances; if a fixed annual percentage change of such failure can be approximated, that risk can be rolled into the total discount rate. A fourth factor is pragmatics: people seem to discount the future anyway, so the theory might as well incorporate a uniform compromise to express