thesisPrototype

Government data

Belgium CPI annual inflation, August 2026 first print

What will Statbel's not-seasonally-adjusted headline consumer price index annual inflation rate (MS_CPI_INFL), base year 2025, for Belgium in August 2026 be on the first Consumer Price Index - Health Index print?

Overdue · was due Sep 3, 2026

The resolver has no route for this target's reference. The target was registered with a generic source link rather than a resolver binding.

NO_ROUTE_GENERIC_URL · resolver status as of Oct 7, 2026

Forecast

3.55%
2.71%–4.4%
80% prediction interval
gpt-5.5Run record ↗

Cumulative probability

Chance that the outcome is at or below each value.

0%25%50%75%100%1.45%3.55%5.67%Forecast value

Shaded band: 80% interval (2.71%–4.4%). Dashed line: point estimate (3.55%).

Derived from the point estimate and 80% interval; the agent did not report a full distribution.

Analysis

§Belgium Statbel CPI headline annual inflation forecast

Framing: this target is Statbel's national not-seasonally-adjusted headline consumer price index annual inflation field MS_CPI_INFL for August 2026, base year 2025, first print. The series is not a human-adjudicated market outcome; it resolves mechanically from Statbel's CPI/health-index release or the matching official open-data file.

▸ Reported tool use: official.open_datamodel report
curl Statbel open-data page for CPI download links
↳ Fetched official Statbel open-data listing: 'Consumer price index and health index', period since 1920, TXT ZIP length 106388 and XLSX length 422150; also 'Indexes by product group' XLSX length 14536586 and ZIP length 5128865.
▸ Reported tool use: official.open_datamodel report
download and parse Statbel CPI All base years TXT from the official ZIP
↳ Fetched Statbel CPI All base years TXT rows for NM_BASE_YR=2025: 2026-02 CPI index 101.72 and MS_CPI_INFL 1.45%; 2026-03 101.84 and 1.65%; 2026-04 103.34 and 4.01%; 2026-05 103.26 and 4.08%; 2026-06 102.95 and 3.40%; 2026-07 103.60 and 3.56%.
▸ Reported tool use: official.calendarmodel report
curl Statbel 2026 calendar around CPI/health-index releases
↳ Fetched Statbel 2026 calendar rows: 2026-07-30 'De inflatie bedraagt 3,56%' for the July CPI release; 2026-08-28 'Consumptieprijsindex - Gezondheidsindex' with period m-2026-08; 2026-09-29 'Consumptieprijsindex - Gezondheidsindex' with period m-2026-09.
▸ Reported tool use: official.forecastmodel report
curl Federal Planning Bureau CPI inflation forecasts page dated 07/07/2026
↳ Fetched FPB national consumer price index path: Jan 2026 1.10%, Feb 1.45%, Mar 1.65%, Apr 4.01%, May 4.08%, Jun 3.40%, Jul forecast 3.37%, Aug forecast 3.35%, Sep forecast 3.55%, and average 2026 inflation 3.1%.

Base rate/reference class: the last 24 Statbel MS_CPI_INFL first-print observations from 2024-08 through 2026-07 have mean 2.68%, range 1.10%-4.08%, and latest 3.56%; the last 12 are 1.91, 2.12, 2.00, 2.40, 2.06, 1.10, 1.45, 1.65, 4.01, 4.08, 3.40, 3.56. For this repeated rate series, last-print persistence at 3.56% is the default prior.

Model candidates: persistence candidate point 3.56, p10 2.72, p50 3.56, p90 4.40, 80% interval [2.72, 4.40], 90% interval [2.47, 4.65], interval method recent-change Gaussian with calibration_n 23 and train cutoff 2026-07. Bias-adjusted FPB candidate uses FPB August 3.35 plus the July forecast miss of +0.19, giving point 3.54 with the same interval method.

Prior/update/interval: persistence prior is 3.56 from Statbel July 2026. Historical sample is the last 24 fetched MS_CPI_INFL values from 2024-08 through 2026-07; successive monthly changes have sigma = 0.659 percentage points, so 1.28*sigma = 0.843 pp. Current update is the FPB August forecast 3.35, adjusted by its July undercall versus Statbel first print (3.56 - 3.37 = +0.19), giving 3.54. Weighting 70% persistence and 30% bias-adjusted FPB gives 0.70*3.56 + 0.30*3.54 = 3.55. Applying the 0.843 half-width gives [2.71, 4.40].

Resolution-date discipline: the registered ledger target fixes resolutionDate at 2026-09-03 and I keep that field. The official Statbel calendar fetched this run lists the m-2026-08 CPI/health-index release on 2026-08-28, so this appears to be a ledger-date discrepancy rather than evidence about the value.

Counter-considerations: upside risk would land above the interval if August repeats an energy or administered-price jump like the March-to-April 2026 move and headline inflation exceeds 4.40%. Downside risk would land below the interval if the July rebound reverses sharply through energy, travel, or communication-price cuts and the first print falls below 2.71%.

Slug check: a curl fetch of https://app.thesisinstitute.org/specs.json returned a 404 HTML page, so I checked the local generated ledger target and registration instead; both contain catalogSlug belgium-cpi-annual-rate-august-2026 and dataPointId statbel.cpi.headline_yoy.2026-08.first_print.

Review disposition: accepted the reviewer suggestion to keep the ledger/calendar discrepancy in reasoning rather than in the resolver rule, and accepted the suggestion to name the 2024-08 through 2026-07 calibration window in the compact interval math step.

Key drivers

  • July first-print persistence at 3.56%
  • FPB August CPI forecast 3.35% before July print
  • FPB July path undercalled Statbel July by 0.19 pp
  • recent first-print changes have 0.659 pp sigma

Tool evidence

This run has no captured tool responses. “Reported tool use” in the analysis is the model’s account, not an archived tool response.

Sources and resolution

Official source
Statbel Consumer Price Index - Health Index release
Resolution date
September 3, 2026· outcome not recorded
Resolution rule
Resolve to Statbel's Consumer Price Index - Health Index first print for m-2026-08: field MS_CPI_INFL for NM_YR=2026, NM_MTH=8, NM_BASE_YR=2025 in the official Consumer price index and health index open-data file or equivalent first release table. Use the first print only, in percent as published; ignore later revisions.
Run details

The analysis is the model’s written report. Tool-use descriptions in that report are model claims; the activity artifacts contain the execution record.

thesis.analyst · gpt-5.5 · full · v2.5.9

pre-submit review · completed

Draft is publishable: it matches the ledger target, uses first-print Statbel resolution, states a persistence/base-rate prior, justifies a small FPB-adjusted update, and has coherent point/interval fields.

  • info optional_suggestion: Consider moving the ledger/calendar date discrepancy out of resolutionRule and keeping it only in reasoning, since the rule itself can stay cleaner while resolutionDate remains 2026-09-03.
  • info optional_suggestion: The interval rationale would be slightly stronger if the exact 24-month calibration window were named as 2024-08 through 2026-07 in the compact math step too.

disposition not applicable: Review disposition: accepted the reviewer suggestion to keep the ledger/calendar discrepancy in reasoning rather than in the resolver rule, and accepted the suggestion to name the 2024-08 through 2026-07 calibration window in the compact interval math step.

disposition not applicable: Review disposition: accepted the reviewer suggestion to keep the ledger/calendar discrepancy in reasoning rather than in the resolver rule, and accepted the suggestion to name the 2024-08 through 2026-07 calibration window in the compact interval math step.

Activity artifacts

Complete original trace

§Belgium Statbel CPI headline annual inflation forecast

Framing: this target is Statbel's national not-seasonally-adjusted headline consumer price index annual inflation field MS_CPI_INFL for August 2026, base year 2025, first print. The series is not a human-adjudicated market outcome; it resolves mechanically from Statbel's CPI/health-index release or the matching official open-data file.

▸ Reported tool use: official.open_datamodel report
curl Statbel open-data page for CPI download links
↳ Fetched official Statbel open-data listing: 'Consumer price index and health index', period since 1920, TXT ZIP length 106388 and XLSX length 422150; also 'Indexes by product group' XLSX length 14536586 and ZIP length 5128865.
▸ Reported tool use: official.open_datamodel report
download and parse Statbel CPI All base years TXT from the official ZIP
↳ Fetched Statbel CPI All base years TXT rows for NM_BASE_YR=2025: 2026-02 CPI index 101.72 and MS_CPI_INFL 1.45%; 2026-03 101.84 and 1.65%; 2026-04 103.34 and 4.01%; 2026-05 103.26 and 4.08%; 2026-06 102.95 and 3.40%; 2026-07 103.60 and 3.56%.
▸ Reported tool use: official.calendarmodel report
curl Statbel 2026 calendar around CPI/health-index releases
↳ Fetched Statbel 2026 calendar rows: 2026-07-30 'De inflatie bedraagt 3,56%' for the July CPI release; 2026-08-28 'Consumptieprijsindex - Gezondheidsindex' with period m-2026-08; 2026-09-29 'Consumptieprijsindex - Gezondheidsindex' with period m-2026-09.
▸ Reported tool use: official.forecastmodel report
curl Federal Planning Bureau CPI inflation forecasts page dated 07/07/2026
↳ Fetched FPB national consumer price index path: Jan 2026 1.10%, Feb 1.45%, Mar 1.65%, Apr 4.01%, May 4.08%, Jun 3.40%, Jul forecast 3.37%, Aug forecast 3.35%, Sep forecast 3.55%, and average 2026 inflation 3.1%.

Base rate/reference class: the last 24 Statbel MS_CPI_INFL first-print observations from 2024-08 through 2026-07 have mean 2.68%, range 1.10%-4.08%, and latest 3.56%; the last 12 are 1.91, 2.12, 2.00, 2.40, 2.06, 1.10, 1.45, 1.65, 4.01, 4.08, 3.40, 3.56. For this repeated rate series, last-print persistence at 3.56% is the default prior.

Model candidates: persistence candidate point 3.56, p10 2.72, p50 3.56, p90 4.40, 80% interval [2.72, 4.40], 90% interval [2.47, 4.65], interval method recent-change Gaussian with calibration_n 23 and train cutoff 2026-07. Bias-adjusted FPB candidate uses FPB August 3.35 plus the July forecast miss of +0.19, giving point 3.54 with the same interval method.

Prior/update/interval: persistence prior is 3.56 from Statbel July 2026. Historical sample is the last 24 fetched MS_CPI_INFL values from 2024-08 through 2026-07; successive monthly changes have sigma = 0.659 percentage points, so 1.28*sigma = 0.843 pp. Current update is the FPB August forecast 3.35, adjusted by its July undercall versus Statbel first print (3.56 - 3.37 = +0.19), giving 3.54. Weighting 70% persistence and 30% bias-adjusted FPB gives 0.70*3.56 + 0.30*3.54 = 3.55. Applying the 0.843 half-width gives [2.71, 4.40].

Resolution-date discipline: the registered ledger target fixes resolutionDate at 2026-09-03 and I keep that field. The official Statbel calendar fetched this run lists the m-2026-08 CPI/health-index release on 2026-08-28, so this appears to be a ledger-date discrepancy rather than evidence about the value.

Counter-considerations: upside risk would land above the interval if August repeats an energy or administered-price jump like the March-to-April 2026 move and headline inflation exceeds 4.40%. Downside risk would land below the interval if the July rebound reverses sharply through energy, travel, or communication-price cuts and the first print falls below 2.71%.

Slug check: a curl fetch of https://app.thesisinstitute.org/specs.json returned a 404 HTML page, so I checked the local generated ledger target and registration instead; both contain catalogSlug belgium-cpi-annual-rate-august-2026 and dataPointId statbel.cpi.headline_yoy.2026-08.first_print.

Review disposition: accepted the reviewer suggestion to keep the ledger/calendar discrepancy in reasoning rather than in the resolver rule, and accepted the suggestion to name the 2024-08 through 2026-07 calibration window in the compact interval math step.

calibrated forecast · 80% CI
3.55%[2.71% · 4.4%]
Target metadata

Data point: statbel.cpi.headline_yoy.2026-08.first_print

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