The devil, according to an old saying, lies in the detail. This is as true for statistical analysis as it is for any other activity.
Take, for example, the latest quarterly employment statistics (QES), released by Statistics SA on Tuesday. As has already been widely reported, the QES for the quarter to December showed an increase in the number of people employed in the non-agricultural business sector of about 90 000 people, compared with the quarter to September, or a gain of about 1.3 percent.
Data, however, can be "sliced" in a number of different ways. The first is with regard to time periods. The QES reports on changes in the number of people employed in two major ways: between the current and previous quarter, such as September and December; and between the current quarter and the corresponding quarter of the previous year, such as December 2004 and December 2005.
For each of these periods (quarter-on-quarter and year-on-year), the QES provides the change in actual numbers employed, as well as the percentage.
The latest QES shows that the number of those employed in formal non-agricultural industries increased by 158 000 or 2.2 percent between December 2004 and December 2005 - an increase from 7.097 million to 7.255 million employees. The increase quarter-on-quarter (between September and December) involved 90 000 employees, or a change of 1.3 percent.
That is not the only way data collected through the QES can be sliced.
community, social and personal services.
For each of these sectors, the change in the number of people employed and the percentage change, quarter-on-quarter and year-on-year, are presented.
Year-on-year, comparing December 2004 with December 2005, all sectors except mining and quarrying, and financial intermediation, insurance, real estate and business services, reported an increase in the number of people employed.
From the quarter to September to the quarter to December, the mining and quarrying industry reported a decrease of 22 000 employees, or 4.8 percent, while the financial intermediation, insurance, real estate and business services industries reported a decrease of 11 000 employees, or 0.7 percent.
Manufacturing reported an annual increase of 21 000 employees, or 1.8 percent. Electricity, gas and water supply showed an annual increase of 3 000 employees, or 7.1 percent, and construction an annual increase of 77 000 employees, or 20.6 percent.
The wholesale and retail trade, repair of motor vehicles, motor cycles and personal and household goods, hotels and restaurants industries reported an annual increase of 43 000 employees, or 3.1 percent; transport, storage and communication an annual increase of 5 000 employees, or 1.6 percent; and finally, the community social and personal services industry reported an annual increase of 42 000 employees, or 2.4 percent.
In the detail, however, other trends can be discerned: while jobs were shed in financial intermediation, insurance, real estate and business services between December 2004 and December 2005, there was a quarterly increase of 30 000 employees, or 2 percent, between the quarters ending in September and December 2005.
And while electricity, gas and water supply reported an annual increase of 7.1 percent for the year to December 2005, compared with December 2004, there was no increase between the quarter to September and the quarter to December.
Not only does the QES measure changes in employment: it reports on gross earnings paid to employees in the formal non-agricultural business sector, again for each of the major industries, quarter-on-quarter and year-on-year, reflecting changes in both numbers and percentages.
Non-agricultural formal sector employment increased by 1.3 percent or 90 000 jobs between the quarter to September and the quarter to December.
However, the QES provides far more information than this, and it is in that detail that serious statistical analysis must be located.
Pali Lehohla is South Africa's statistician-general and head of Statistics SA. For more information on Stats SA and its statistical outputs, including the latest release on quarterly employment statistics, visit www.statssa.gov.za or contact user services on (012) 310 8600.