Markets and the media tend to focus attention on the economic statistics released regularly by Statistics SA.
Consumer and producer price indices (CPI and PPI) invariably make headlines, as do the quarterly estimates of gross domestic product (GDP).
The link between the setting of interest rates by the Reserve Bank and the movement in the CPIX, which excludes mortgage rates, is often debated by financial and economic analysts.
Yesterday's release of July CPIX data, showing a lower-than-anticipated annual increase of 4.2 percent (and a decrease of 0.8 percent compared with June), will no doubt generate speculation over the further movement of interest rates.
Other statistics are, however, no less important in what they indicate.
For example, at the end of last month, Stats SA released the 2004 mid-year population estimates. As part of its adherence to the International Monetary Fund's special data dissemination standard, Stats SA publishes population estimates for the country as a whole and the nine provinces annually.
This is particularly important in the years between each population census.
In mid-2004, the population was estimated at 46.6 million, an increase of 1.8 million over the October 2001 census figure.
Fifty-one percent of the population is female. Provincial estimates show that KwaZulu-Natal has the largest share of the population (20.7 percent), followed by Gauteng (19 percent). Northern Cape has the smallest share (1.9 percent).
Although there are crude estimation methods, such as inflating the total population at one date by an assumed overall annual growth rate, most serious estimation efforts use the cohort-component approach.
In this method, the population at the start date is disaggregated by sex and age.
The initial population, in this case the 2001 population census, is projected forward by applying age-specific fertility, mortality and migration schedules.
Separate mortality schedules for males and females are applied to each age group.
The result is the population estimated by sex and age at a point in time.
From this estimate a number of useful things can be calculated, including the number of working people in the working ages. The estimates can also be used as the denominator to calculate GDP per capita.
The latest mid-year estimate implies that the per capita GDP should be slightly adjusted upwards as the population growth rate has declined slightly.
It also suggests positive net migration will lead to substantial growth in Gauteng and the Western Cape in the short term.
For Gauteng, it is estimated that 850 000 people will move to the province and 350 000 will move out of the province between 2001 and 2006, resulting in net positive migration of 500 000.
For the Western Cape, the estimated net migration for the same period is 225 000 people, while it is projected that KwaZulu-Natal will have a negative net migration.
These interprovincial shifts in the population suggest that Gauteng might become the most populous province by 2011, when the next full population census takes place.
There has been much concern about the effect of HIV on fertility in South Africa.
There is evidence that being HIV positive lowers the biological ability of women to have children.
There are also arguments that behavioural changes among persons who are HIV positive might impact on fertility rates.
However, fertility in South Africa has been declining since the 1970s.
Given that fertility in South Africa declined from the mid-1980s to the mid-1990s by an average of 15 percent a year, and declined further between 1996 and 2001, the estimates suggests that the overall impact of HIV on the level of fertility is unlikely to be large in comparison with other factors.
There has also been some controversy over the impact of HIV on mortality. The mid-year estimates indicate that the HIV-positive population in 2004 is 3.83 million, or an HIV-prevalence rate of about 15 percent of the adult population.
This is based on empirical data from the causes of death study released by Stats SA in 2002 and the Human Sciences Research Council study on HIV.
Together with the data from ante-natal clinics, these studies provide the only empirical evidence about HIV/Aids in South Africa.
The accumulated Aids deaths up to 2004 were estimated at 1.49 million. However, Stats SA assumptions regarding HIV/Aids may change with the completion of a study on the causes of death.
Pali Lehohla is South Africa's statistician-general and the head of Statistics SA.
For more information on Stats SA and its statistical outputs, including the latest population estimates and yesterday's release of July CPI, visit www.statssa.gov.za, or call user services on (012) 310-8600.