Data comparison over time is central to official statistics
28 Oct '06
2 min read
Official statistics generally measure more than one data point in time, rather than presenting a single number or percentage. This allows for the measurement of change and the identification of trends.
An economic indicators present rate of change over specified periods - inflation in one month is compared with a previous month (month on month).
This is demonstrated well in yesterday's release of the latest consumer price index (CPI) data, where it was reported that the official inflation rate (the percentage change in the CPI for the historical metropolitan areas at September this year compared with that of September last year) was 5.3 percent.
This is 0.1 percentage points lower than the annual rate of 5.4 percent in August.
Even when a specific statistic is presented, such as the size of the population measured through a full population census, this is compared with one or more previous censuses and indicates change in population size.
Stats SA compares data over time. Sometimes this involves measuring the same phenomenon, such as mining sales or wholesale trade sales. In other cases, merging of data is undertaken, where information from different data sets is integrated to measure complex phenomena such as poverty, or to construct multidimensional indices measuring deprivation or human development. Estimation of gross domestic product (GDP) involves a similar integration and comparison of multiple data sources.
Stats SA updates time-series data for a set of key economic indicators such as the CPI and GDP. This allows for the long-term comparison of data so that change can be measured and trends identified.
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