Last week I raised a number of issues about the way statistical data are used, especially in regard to the formulation, implementation and impact monitoring of social and economic policy. In doing this, I suggested that data are most valuable when difficult questions are raised and debated as a result of careful analysis. An overview of some of the data released by Statistics SA over the past week demonstrates this well.
Last week's release of February's motor trade sales reported that the strong growth in this sector had continued, with motor trade sales rising 14 percent compared with February last year.
Motor trade sales are one of many elements used in the compilation of gross domestic product. However, proper use of the data involves more than citing a figure (14 percent) in support of views that are already established.
Motor trade sales are derived from the performance of a number of activities in the sector: new vehicle sales, used vehicle sales, sales of fuel, workshop income, income from the sale of accessories, and convenience store sales.
Each has a different weight, reflecting the contribution of each activity to the motor trade sales. For example, new vehicle sales contribute 36.6 percent to total motor trade sales, while fuel sales contribute 18.7 percent and sales of used vehicles 17.9 percent.
At a general level of interpretation, policy analysts might conclude that a year-on-year increase of 14 percent in motor trade sales reflects strong economic growth.
However, more detailed analyses of the data would lead to questions about the contribution of each activity in overall motor trade sales.
What do sales of new vehicles contribute to this growth How do they compare with the sales of used vehicles What is the contribution of fuel sales to the rise How much of this is the result of higher fuel price, rather than higher consumption?
Similar questions can be raised through a study of the statistics on civil cases for debt for February, released last week.
This showed a decrease in civil summonses issued for debt for the three months to February, compared with the same period last year (minus 4.4 percent); and in civil judgments recorded for debt for the same period (minus 9 percent).
More value could be added to this analysis by exploring the geographical breakdown of summonses and judgments.
What are the differences in debt profile between metropolitan areas and smaller towns, urban and rural areas, villages and suburbs?
How do these profiles change when summonses and judgments are broken into components, such as debt related to goods sold, services rendered, money lent, credit card and refer to drawer cheque debt The value of the data is enhanced when it is used to ask probing questions?
This week's release of the consumer price index (CPI) for last month reported a headline inflation rate (year on year) rise of 0.4 percentage point from the 5.7 percent rise in February. The year-on-year increase in the CPIX (CPI excluding mortgages) for last month was 0.6 percentage point higher than the 4.9 percent increase in February.
The annual change of 5.5 percent in CPIX, the monetary policy inflation target measure, brought this measure closer to the top end of the range of the Reserve Bank's inflation target range (between 3 percent and 6 percent), and will be interrogated thoroughly by monetary policy analysts.
The year-on-year rise in the headline CPI inflation rate of 6.1 percent will also be subject to intense scrutiny.
Again, these single-figure indicators are based on a depth of rich data.
For example, policy analysts will be interested to note that some of the main drivers of year-on-year consumer price inflation this month were the CPI for education, for which the rate rose to 8 percent last month from 7 percent in February; CPI for household operation, for which the rate increased to 7.3 percent from 5.2 percent; and CPI for transport, for which the rate rose to 4.6 percent from 2.1 percent.
Despite prerelease speculation that the CPI for food had increased dramatically, the data revealed a decrease in food inflation, from 8 percent in February to 7.7 percent last month. CPI for meat fell to 12.7 percent from 15 percent.
This overview of three of Stats SA's statistical releases - CPI, motor trade sales and civil cases for debt - demonstrates the overall point well: data must be interrogated in detail for its full use to be exploited.
Pali Lehohla is South Africa's statistician-general and head of Statistics SA. For more information, visit www.statssa.gov.