An updated Retail Sales Index (RSI) has been introduced in the January 2018 release. The underlying methodology remains unchanged. The index is primarily intended to measure short-term trends. For long term analysis, allowance must be made for the fact that the series does not reflect changes in retail structures between updates.
This set of monthly retail sales indices has been compiled with reference to base year 2015=100. The underlying structural weighting system is mainly based on the 2015 Annual Services Inquiry. Weights are updated from year to year using ratios of average weekly turnover by size class within business type.
The Retail Sales Index covers, on a matched sample basis, the retail sales of retail businesses, wholesale businesses with sizeable retailing activity, and the separate sales establishments of non-distribution enterprises. Excluded from the index coverage are the direct retail sales from non-distribution establishments together with the incidental retail sales of wholesale businesses. Also excluded are sales by hawkers, street stalls, and other retailing activities not conducted from permanent business premises. The RSI does include internet/online sales of enterprises which have a presence in Ireland, but these sales are included under the primary activity of the enterprise, e.g. online grocery sales are included in Non-Specialised Stores. The statistical unit used for reporting sales figures in this inquiry is the enterprise (i.e. complete business covering all branches). Online retailers not registered in Ireland but selling to Irish Residents are not within the scope of the Irish RSI.
The business categories are based mainly on the Statistical Classification of Economic Activities in the European Community (NACE Rev. 2). The index system is structured on the retailing enterprises covered in the 2015 Annual Services Inquiry classified by 13 retail business categories and four turnover (excluding VAT) ranges. The following NACE Rev.2 categories apply:
For a full NACE Rev2 breakdown of the above categories see Classifications on our website.
The value indices are calculated by updating the aggregate 2015 retail turnover (including VAT) of these enterprises in these cells using the monthly retail sales data provided by the enterprise respondent panel from 2015 onwards.
The compilation of the index for a current month is based on the percentage change in average weekly sales in these cells over the corresponding monthly period of the previous year. The monthly volume indices are calculated by deflating the seasonally unadjusted value indices by specially constructed retail price indices derived from the Consumer Price Index (CPI). Further details of the Retail Sales Index methodology is available on our website.
All Retail Sales “unadjusted” series are trading day adjusted as they are based on either a standardised four or five-week reporting period (see reference period note above). Seasonal adjustment is conducted using the direct seasonal adjustment approach. Under this approach each individual series is independently adjusted, e.g. aggregate series are adjusted without reference to the component series. A consequence of the direct seasonal adjustment is that there can be a loss of additivity in the series. Each individual seasonally adjusted series is calculated based on unadjusted data spanning from January 2010 to the current period.
The adjustments are completed by applying the X-13-ARIMA model, developed by the U.S. Census Bureau, to the unadjusted data. For additional information on the use of X-13ARIMA-SEATS see (Findley, D.F., B.C. Monsell, W.R. Bell, M.C. Otto, and B. Chen (1998), “New Capabilities and Methods of the X-12-Arima Seasonal Adjustment Program”, Journal of Business & Economic Statistics, 16, pp. 127-177.) and Win X-13
This methodology estimates seasonal factors while also taking into consideration factors that impact on the quality of the seasonal adjustment, such as:
Note: The Motor Trade group comprises all retail motor trade activities, of which new car sales accounts for approximately 70% of turnover.
COVID-19 note
Seasonally adjusting the Retail Sales Index will be challenging until the scale and shape of the impact of COVID-19 on the time series is better understood. Each month the outliers are reviewed and updated as required. 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 seasonal adjusted series.
Rebase 2015
The rebasing of the series is in line with EU recommendations to update the base reference periods at regular five-year intervals. This new series replaces the existing series to base year 2010 as 100.
The difference in the new rebased RSI series is the use of new cell and sector baseweights taken from the ASI 2015. The existing cell structure/breakdown was maintained in this series.
The new baseweights are updated each month using changes to respondents’ monthly turnover. The rebase also includes the reclassification of enterprises based on their current product profile.
Online Sales
The collection of data for online turnover began in November 2018. Enterprises in the sample provide the value of their online turnover for the reporting period. As for all of the survey only Enterprises registered in Ireland are included. From the Annual Services Inquiry (2017) the Online and Mail Order Sector (G4791) registered in Ireland is estimated at 1.0% of all Retail Businesses. A fixed base weight is used from the Annual Services Inquiry (2017).
International Comparisons
See Eurostat for International comparisons.
