To assess a health system, one must measure five things: the overall level of health; the
distribution of health in the population; the overall level of responsiveness; the distribution
of responsiveness; and the distribution of financial contribution. For each one, WHO has
used existing sources or newly generated data to calculate measures of attainment for the
countries where information could be obtained. These data were also used to estimate
values when particular numbers were judged unreliable, and to estimate attainment and
performance for all other Member States. Several of these measures are novel and are
explained in detail in the Statistical Annex, where all the estimates are given, along with
intervals expressing the uncertainty or degree of confidence in the point estimate. The correct
value for any indicator is estimated to have an 80% probability of falling within the
uncertainty interval, with chances of 10% each of falling below the low value or above the
high one. This recognition of inexactness underscores the importance of getting more and
better data on all the basic indicators of population health, responsiveness and fairness in
financial contribution, a task which forms part of WHO’s continuing programme of work.