Indeed, while an increase in the share of older age groups tends to boost health-care spending because health needs increase with age, longevity gains could translate into “healthy ageing". For long-term care, however, there may be less of an offset: extra longevity is unlikely to reduce dependency, and long-term care costs are concentrated on the very old age groups, whose numbers will increase the most. The reason why income gains on their own might not generate tremendous pressure is related to the size of the aggregate elasticity of health expenditure per capita to GDP per capita. The hypothesis that health care is a "superior" good is generally rejected based on micro-data analysis where health spending is found to be relatively inelastic to individual income (implying that health is a “necessity", even though estimates might be blurred by the extent of insurance coverage). Moreover, evidence that the aggregate elasticity is significantly greater than unity is not very robust (see Oliveira Martins and de la Maisonneuve, 2006, Annex 2B). As a result, long-term financial simulations generally assume an aggregate income elasticity within the range of 1.0-1.2.