Some communities prefer to create virtual insurance amongst themselves by other means than contractual risk transfer, which assigns explicit numerical values to risk. A number of religious groups, including the Amish and some Muslim groups, depend on support provided by their communities when disasters strike. The risk presented by any given person is assumed collectively by the community who all bear the cost of rebuilding lost property and supporting people whose needs are suddenly greater after a loss of some kind. In supportive communities where others can be trusted to follow community leaders, this tacit form of insurance can work. In this manner the community can even out the extreme differences in insurability that exist among its members. Some further justification is also provided by invoking the moral hazard of explicit insurance contracts.
Limited risk of catastrophically large losses: Insurable losses are ideally independent and non-catastrophic, meaning that the losses do not happen all at once and individual losses are not severe enough to bankrupt the insurer; insurers may prefer to limit their exposure to a loss from a single event to some small portion of their capital base. Capital constrains insurers' ability to sell earthquake insurance as well as wind insurance in hurricane zones. In the United States, flood risk is insured by the federal government. In commercial fire insurance, it is possible to find single properties whose total exposed value is well in excess of any individual insurer's capital constraint. Such properties are generally shared among several insurers, or are insured by a single insurer who syndicates the risk into the reinsurance market.