Data for the Retail Sales Index (RSI) is collected monthly from a sample of 1,600 retail enterprises. Despite difficult circumstances, many retailers have continued to supply us with information and we wish to thank all survey respondents for their ongoing support.
However, due to temporary closures and on-going difficulties faced by some businesses, the response rate for the August 2020 RSI was about two percentage points lower than the corresponding month last year.
The Retail Sales index is based on a matched sample of enterprises in consecutive months. Imputation is not normally carried out for smaller enterprises which have not returned data. In each sector key companies are identified based on their significance to the sector (turnover). If key company data is not received on time for the Provisional results, then an estimate is made using trends from other similar companies and from other available data sources.
Auxiliary data sources have also been used to validate the results for August 2020 at retail business sector level. The CSO is satisfied that this range of information supports the trends estimated in the Retail Sales Index for August. The auxiliary sources used for imputation and validation purposes included:
The spending patterns since March 2020 have been an exception to the existing seasonal patterns. Seasonally adjusting the Retail Sales Index will be challenging until the scale and shape of the impact COVID-19 has on the time series is better understood. The seasonal adjustment models have been reviewed each month since March 2020 and have been changed as appropriate. Users should be aware that further observations, as data becomes available in the months ahead, and revisions to the seasonal adjustment models may result in revisions to the seasonally adjusted series.
The CSO wishes to thank all those enterprises who supplied their retail sales data for August and urge them to continue to do so for September and future months. Even if turnover is nil or very low, such information is still required to measure the trend in sales in each retail sector. The CSO will continue to monitor the range of supplementary information described above to derive the best estimate for retail sales in September. The September Retail Sales Index is planned for publication on 28th October.