Retail supplementary information

Supplementary information for the Retail Sales Index.

The Northern Ireland Retail Sales Index (RSI) was first published on 16 March 2022 as an experimental index.

Overview of the Northern Ireland Retail Sales Index

The RSI is published quarterly and is designed to provide a general measure of changes in the output of the retail sales sector in Northern Ireland. The retail sales sector is a subset of the Index of Services (IOS) and refers to SIC 47 (Retail trade, except of motor vehicles and motorcycles).

The quarterly RSI Statistics Bulletin presents the latest seasonally adjusted estimates from the NI Retail Sales Index including comparison with published figures for Great Britain.

The RSI sample is a subset of the overall IOS sample. The IOS sample size is approximately 3,600 businesses within the private sector services industries, drawn on a SIC07 basis; The current RSI sample size is approximately 360 businesses, which accounts for 66% of known retail turnover.

The sample of service industries is selected directly from the Inter Departmental Business Register (IDBR), by stratifying companies by industry and company size. The sample consists of a census of dominant companies and a Neyman stratified random sample of the remaining medium and smaller businesses, which are normally selected on a rotational basis. The sample has been designed to give sufficiently accurate results on the performance of the NI economy whilst ensuring burden on businesses is kept to a minimum.

The census element consists of all companies employing 100 or more employees and those employing 0 to 99 employees and having a turnover of £10 million or more. It is desirable to include these low employment high turnover companies in the sample in order to provide a more comprehensive picture of the overall economy.

The RSI is based on up-to-date information about the output and sales of the services industry. The index is published in March, June, September and December each year and refers to the quarter ending some 11 weeks earlier. 

All series are measured at constant market price (2019 = 100) and are seasonally adjusted using X-13 ARIMA SEATS in order to obtain a clear picture of the general trend.  Deflators adjust the value series to take out the effect of price change to give the volume series. 

Data is collected from the combined Quarterly Business Survey with companies are asked to provide employment and turnover information at the same time. This combined survey form, coupled with the roll-out of an ‘eForm’ (designed to collect data electronically) is intended to reduce the burden to businesses receiving two separate forms at different times.

ONS deflation methodology

Further information