The risk to which a pension fund or life insurance company could be exposed as a result of higher-than-expected payout ratios. Longevity risk exists due to the increasing life expectancy trends among policy holders and pensioners, and can result in payout levels that are higher than what a company or fund originally accounts for. The types of plans exposed to the greatest levels of longevity risk are defined-benefit pension plans and annuities, which guarantee lifetime benefits for policy or plan holders. Average life expectancy figures are on the rise, but even a very small change in life expectancies can create severe solvency issues for pension plans and insurance companies. Precise measurements of longevity risk are still unattainable because the limit of medicine and its impact on life expectancies has not been quantified.