Index-based insurance, also known as index-linked insurance or, simply, index insurance, is primarily used in agriculture. Because of the high cost of assessing losses, traditional insurance based on paying indemnities for actual losses incurred is usually not viable, particularly for smallholders in developing countries. With index-based insurance, payouts are related to an “index” that is closely correlated to agricultural production losses, such as one based on rainfall, yield or vegetation levels (e.g. pasture for livestock). Payouts are made when the index exceeds a certain threshold, often referred to as a “trigger”. Index-based insurance is not therefore designed to protect farmers against every peril, but only where there is a widespread risk that significantly influences a farmer’s livelihood. Many such indices now make use of satellite imagery. Justification for index-based insurance Insuring risk in small-scale agriculture faces particular problems that are not usually encountered by the broader insurance sector. Production relies on natural conditions, such as rain, temperature, and sunlight, which cannot be controlled easily by poorer farmers, other than by those with access to irrigation or plastic tunnels in the case of horticultural crops. Consequently farmers face problems on a regular basis. Unlike other insurance, adverse events cannot easily be predicted statistically, large numbers of people tend to be affected at the same time (known as "covariance" by the insurance industry) and losses for each of them tend to be significant. The opposite is the case for more traditional insurance such as home theft insurance, where actuaries can make a good forecast of the likely incidence of claims, thefts are (relatively) rare, all the houses on a block are not entered at the same time, and entire contents of a house are not usually stolen. Traditional insurance has two cost categories. First is the underlying risk that is being insured and, second, the costs involved in operating the insurance, such as carrying out individual risk assessments and loss adjustments. In the agricultural sector these costs tend to be high and premiums are often unaffordable for most poorer farmers. The fixed costs of loss verification make it uneconomic to investigate losses for small-scale agriculture producers whose total insurance premium are small. In practice, this can lead to poor loss verification, morally hazardous behavior and high loss ratios for insurance companies. In theory, index-based insurance can cover many farmers while avoiding the need for loss assessment and adjustment. This can reduce some