Implied Price Deflator

Within the ONS Retail Sales Index, each retail sector carries value, volume and implied price deflator indices. The deflator is the price component recovered from the other two - value divided by volume - published as its own NSA series with its own CDID. The cataloged record for the Retail Industry release lists the 'Implied Price Deflator' field for AGG 5 textile, clothing and footwear stores under CDID N3DP, with an example value of 112.4.

That granularity is the point: apparel price dynamics differ from grocery or fuel, and a sector-specific deflator keeps fashion margin analysis honest. Index levels are referenced to a base period, so the 112.4 figure is meaningful as growth relative to that base, not as a price level.

Deflate with the wrong sector and real growth is fiction: applying an all-retail deflator to clothing sales during discounting cycles misstates volumes by exactly the margin between baskets. Because the series is non-seasonally adjusted, comparing December to January without seasonal treatment reads clearance sales as price collapses.

Reference-base confusion causes quieter damage - treating an index like 112.4 as a pound price rather than a ratio to base, or splicing pre- and post-rebasing vintages without rescaling. Since CDIDs identify precise series (N3DP here), analyses that cite only 'the ONS deflator' become unreproducible when the release updates.

1. Quote the CDID. Cite N3DP for AGG 5 textile/clothing/footwear rather than a generic deflator, so updates land in the right slot - see ons cdid.
2. Respect the NSA basis. This series is non-seasonally adjusted; apply your own seasonal adjustment before month-on-month conclusions.
3. Anchor interpretations to the base period. Read 112.4 as percent-of-base, not currency; state the reference year in every chart.
4. Pair with the sector's volume series. Real growth requires the matching AGG 5 volume index from the retail sales index release - mismatched sectors corrupt the division.
5. Recompute on rebasing. When ONS re-references the RSI, rebuild deflator histories rather than appending new vintages to old ones.

Adjacent concepts worth reading next: ons-cdid and retail-sales-index.

Sector hubs: apparel-retail data, homefurnishing-retail data.