sahr2001 - Health Systems Trust

17 • Health and Related Indicators
General Indicator-related definitions
Proportion: The relation of a subgroup to the entire group; that is the subgroup
divided by the entire group. Often proportions are actually expressed as
percentages, by multiplying by 100.
Rate: The frequency of events in a population during a specified time period
(usually a year) divided by the population ‘at risk’ of the event occurring
during that time period. Rates tell how common it is for a given event to
occur. Rates are often expressed per 1000 population. Crude rates are
computed for an entire population, while specific rates may be computed for
subgroups such as certain age groups.
Ratio: The relation of one population subgroup to the total population or to
another subgroup; that is, one subgroup divided by another.
Incidence: the number of new cases arising in a given period in a specified
population.
Prevalence: the number of cases in a defined population at a specified point
in time.
Demographic Indicators
The primary source of in-country data is the Census. Although the population
figures quoted in this section are derived from the 1996 Census, Statistics SA
issues exponential growth and adjustment factors that allow for estimates
for later years to be calculated. What must be borne in mind when using any
population figures, is that they involve a high degree of uncertainty.
In the face of such uncertainty, some might consider it prudent to make no
projections at all, but, as Lutz et al argue: “in the face of the overwhelming
humanitarian, social and economic challenges facing South Africa,
(population) projections are more urgently needed for planning than in many
countries having more accurate data and less discontinuous trends” [SA
Uncertain Demographics]. a This section has drawn on a number of models
that have sought to accommodate these uncertainties:
◆ The StatsSA mid-year estimates from 2000 include scenarios that ignore
the impact of HIV/AIDS (‘Without AIDS’) or attempt to take into
account the additional deaths that might have occurred due to HIV/
AIDS (‘With AIDS’). These estimates are based on the translation of
the antenatal sero-prevalence data to ‘additional deaths due to HIV/
AIDS’, using several assumptions outlined in the 2000 P0302 Statistical
Release.
◆ The Actuarial Society of South Africa (ASSA) has developed a series of
models - this section has used outputs from the ASSA2000 model.
a
The full reference for short references given in square brackets are at the end of the
chapter
285