HELPERG Data · Guide · Economic data

Preliminary values and revisions: why a published economic figure can change

Flash estimates, late reports and new seasonal factors revise official figures. How BLS revises CPI and PPI, how Eurostat revises GDP, and how HELPERG shows a value that replaced another.

The short answer

Statistical agencies publish early so the figures are useful. Early means incomplete: some reports arrive late, seasonal patterns are re-estimated, and fuller source data replaces early estimates. When that happens, the agency publishes a revised value for the same reference period. That is not new information about a new month; it replaces the old figure for that month. Each agency publishes when and how its figures can be revised.

When the main series are revised

Revision practice of BLS and Eurostat for CPI, PPI and GDP, from their own documentation
Series	First published as	What can change later
BLS CPI-U and CPI-W, not seasonally adjusted	final	BLS treats these indexes as final when issued.
BLS CPI, seasonally adjusted	monthly value	Seasonal factors are recalculated each year when January data are released in February. That can revise seasonally adjusted indexes for the previous five years.
BLS PPI	first issuance	Since the November 2021 data, BLS updates the indexes in each of the three interim months after first issuance, and posts the final indexes four months after original publication. Separately, seasonally adjusted indexes are recalculated each year, going back five years.
Eurostat GDP, EU and euro area	preliminary flash estimate, about 30 days after the quarter	A flash estimate follows at about 45 days, then regular estimates at about 65 and 110 days. The flash estimates revise only the latest quarter.
Eurostat inflation (HICP), euro area	flash estimate	A full HICP release follows the flash estimate. HELPERG’s calendar lists both release dates, but HELPERG publishes no flash value: its HICP figure is the annual rate from the full release. To compare the flash figure with the full one, read both Eurostat releases.

A dated example from the source: Eurostat’s GDP release of 30 July 2026 said its figures might be revised with the flash estimate of 14 August 2026, and by the regular estimates of 7 September and 20 October 2026.

How to read a revision

Same reference period. Compare “September as first published” with “September as revised”, not with October.
Points and percent. A monthly change revised from 0.2% to 0.3% moved by 0.1 percentage point. Measured against the first figure, the rate is 50% higher (0.3 ÷ 0.2 − 1 = 0.5). Prices themselves rose 0.3% in that month instead of 0.2%.
Seasonally adjusted or not. Seasonal-factor updates move adjusted series. An unadjusted series can stay as first published.
Note when you read it. A figure is a vintage: the value as published on a date. Two people quoting different numbers for the same month may both be right, a month apart.

Illustrative, not published data. A monthly change first published as +0.2% for September is shown a month later as +0.3%. September’s value changed. October’s figure is a separate release.

How HELPERG shows a revised value

The economic releases page and the economic calendar show the current value for each reference period. A value that replaced a different one is marked as a revision and shows what it replaced.
The economic data API serves the current vintage of each reference period, with revisionCount saying how many times it changed. Earlier vintages stay in storage and are not served by any public endpoint.
Each record keeps three kinds of time apart: the publisher’s time, the time HELPERG’s scheduled run recorded the figure, and the time HELPERG’s index was last rebuilt. The last one moves on every scheduled run, whether or not a value changed. A moved timestamp is not a revision.

For what the two price indexes measure, and how their monthly and 12-month changes are computed, see CPI vs PPI.

Sources

The publishers’ own documentation. Where this guide describes HELPERG’s behaviour, the reference is HELPERG’s API documentation, linked in the text.

Seasonal adjustment in the CPI: annual recalculation of seasonal factors — U.S. Bureau of Labor Statistics
CPI frequently asked questions — U.S. Bureau of Labor Statistics
Handbook of Methods, Producer Price Indexes: presentation and revisions — U.S. Bureau of Labor Statistics
Main aggregates: flash and regular estimates of GDP — Eurostat
Preliminary GDP flash estimate in 30 days for Europe — Eurostat
Euro indicators release of 30 July 2026 (GDP, second quarter 2026) — Eurostat

See released values and their revisions All data guides

Also in the guides: Reading an hourly weather forecast · Weather forecast vs observations.