This week Statistics SA released the results of two surveys that measure important levels and trends in the economy and provide key inputs in the calculation of gross domestic product (GDP).
The monthly mining production and sales survey covers all mining establishments operating in the economy.
The results of this survey are used to calculate physical volume of mining production indices in order to estimate GDP and its components.
Results of the monthly manufacturing production and sales survey, also released this week, are used to calculate indices of the physical volume of manufacturing production.
These provide an indicator of the real level of manufacturing activity. They are used in monitoring the state of the economy and formulation of policy, and also provide important inputs to the estimation of the GDP.
According to the mining survey, total mining production for the third quarter of 2004, after seasonal adjustment, increased by 4.3 percent compared with the second quarter of 2004.
This increase was because of a seasonally adjusted increase of 5.7 percent in the production of non-gold minerals. But the rise was slightly counteracted by a seasonally adjusted decrease of 1.6 percent in production of gold.
The 5.7 percent rise was mainly because of an increase in the production of platinum group metals (up 2.1 percentage points), diamonds (up 1.3 percentage points), other non-metals (up 0.8 of a percentage point) and other metals (up 0.2 of a percentage point).
The seasonally adjusted value of mineral sales at current prices for the three months to August reflected a decrease of 2 percent compared with the previous three months.
But the actual value of mineral sales at current prices for the three months to August rose by 3.6 percent compared with the three months to August 2003.
The 2 percent fall can be attributed to a decrease of 9.8 percent, or R762.1 million, in sales of gold. But this decrease was counteracted by an increase of 0.6 percent, or R144.2 million, in sales of non-gold minerals.
Seasonal adjustment is a means of removing the estimated effects of normal seasonal variation so that the other influences can be more clearly recognised.
The seasonal adjustment does not aim to remove irregular or non-seasonal influences which may be present in any particular month.
The value of sales of manufactured products is obtained monthly from the sample of just over 3 000 enterprises, drawn from a population of about 31 000 manufacturing enterprises.
Each manufacturing division is divided into four size groups. All large enterprises (size group one), which comprise about one-third of the enterprises in the current sample, are completely enumerated.
Simple random sampling is applied for size group two (medium-sized enterprises), and for size groups three and four (small enterprises).
The total value of sales of manufactured products of large enterprises in a division is added to the weighted totals of size groups two, three and four of that division to reflect the total value of sales of the division.
The results of the latest manufacturing survey show that production for the third quarter increased by 2.7 percent, after seasonal adjustment, compared with the second quarter of the year. Higher production was reported by nine of the 10 manufacturing divisions.
The major contributor to the increase was the food and beverage division (contributing 1 percentage point to total manufacturing production), followed by the motor vehicles, parts and accessories and other transport equipment division (contributing 0.8 of a percentage point).
The total value of sales of manufactured products at current prices for the third quarter of 2004 increased by 2.8 percent (R5.412 billion), after seasonal adjustment, compared with the second quarter of 2004.
High-profile indicators measuring, for example, consumer and producer inflation, invariably attract considerable attention.
But the results of surveys measuring production and sales in the various economic sectors are important indicators of economic trends, and influence the calculation of GDP.
Pali Lehohla is South Africa's statistician-general and head of Statistics SA. For more information on Stats SA and its statistical outputs, including production and sales for mining and manufacturing.