Fig. 1

Illustration and interpretation of descending cumulative distribution functions for catastrophic health expenditures.

All figures show a descending cumulative distribution function of OOP shares on health in household resources (also referred to as a ‘catastrophic incidence curve’). The y-axis represents the proportion of the population whose OOP shares on health in household resources meet or exceed threshold τ, and the x-axis shows the range of catastrophic thresholds τ. Any point on the curve can thus be interpreted as the incidence rate of catastrophic health expenditures for a given threshold. In (a), the cumulative distribution function shows that 15% of the population are spending 25% or more of household resources on OOP payments for health. In (b), Country A is said to exhibit dominance over Country B given its catastrophic incidence curve is always below that of Country A. In other words, the proportion of its population facing catastrophic health expenditures (y-axis) is always lower than Country B, no matter the threshold (x-axis). In (c), Country A and Country B exhibit non-dominance due to intersection given their catastrophic incidence curves intersect at the 12% threshold. This means that the proportion of the population in Country A facing catastrophic health expenditures is lower than Country B for thresholds below 12% but is higher than Country B for thresholds above 12%. In (d), Country A and Country B exhibit non-dominance due to insignificance given their catastrophic incidence curves differ but not to a statistically significant degree. This means that the proportion of the population in Country A facing catastrophic health expenditures differs from the proportion of the population in Country B facing catastrophic health expenditures but the difference is insignificant