In other places people are denied treatment because of personal lack of funds, or because of decisions made by insurance companies. The American Supreme Court approved paying doctors to ration care, saying that there must be "some incentive connecting physician reward with treatment rationing". Shortages of organs for donation forces the rationing of organs for transplant even where funding is available. See also Healthcare rationing in the United States  The concept in economics and banking of credit rationing describes the situation when a bank limits the supply of loans, although it has enough funds to loan out, and the supply of loans has not yet equalled the demand of prospective borrowers. Changing the price of the loans (interest rate) does not equilibrate the demand and supply of the loans. Personal carbon trading refers to proposed emissions trading schemes under which emissions credits are allocated to adult individuals on a (broadly) equal per capita basis, within national carbon budgets. Individuals then surrender these credits when buying fuel or electricity. Individuals wanting or needing to emit at a level above that permitted by their initial allocation would be able to engage in emissions trading and purchase additional credits. Conversely, those individuals who emit at a level below that permitted by their initial allocation have the opportunity to sell their surplus credits. Thus, individual trading under Personal Carbon Trading is similar to the trading of companies under EU ETS. Personal carbon trading is sometimes confused with carbon offsetting due to the similar notion of paying for emissions allowances, but is a quite different concept designed to be mandatory and to guarantee that nations achieve their domestic carbon emissions targets (rather than attempting to do so via international trading or offsetting). The purpose of rationing is to guarantee a minimum of some resource or to impose a maximum to its use. (The latter is the case with carbon rationing, where the scarcity is artificial.) Usually, government determines a fair ration, for example, one proportional to the number of family members. At other times, the ration can only be estimated by the beneficiary, like a factory for which energy is to be rationed. In such cases, a mechanism is needed to discourage misreporting the needs or wants (strategy-proofness). Suppose every participant reports an ideal ration. For so-called uniform rationing, each ration is set to the minimum of the participant's ideal ration and a cap, the cap being determined so that the sum of the rations equals the amount available. So, loosely speaking, the participant asking least will be served first. This mechanism is strategy-proof, avoids unnecessary waste (Pareto optimality) and equally treats equals (anonimity).