FinObservatory /reserves layer: methodology

How the reserve-currency composition page is built, what it shows, and every caveat that bears on reading it. Full retrieval detail (exact URLs, byte and line counts, the fetch/build scripts) lives in data/raw/cofer/SOURCE.md and is summarized in docs/data_provenance.md ("FinObservatory reserve-currency composition layer"). This doc is the reader-facing companion to the page at /reserves.

What this layer is

The currency composition of the world's allocated official foreign-exchange reserves, quarterly from 1999-Q1 to the latest published quarter, for five currencies: the US dollar (USD), euro (EUR), Japanese yen (JPY), pound sterling (GBP), and Chinese renminbi (CNY). Every figure on the page is read directly from data/parquet/cofer.parquet at request time (functions in src/lib/reserves.ts); nothing is hardcoded, so the page updates with each data refresh.

Source

Dataset. IMF Statistics Department, Currency Composition of Official Foreign Exchange Reserves (COFER), dataflow IMF.STA:COFER(7.0.1). Retrieved 2026-07-10 via the IMF SDMX 2.1 REST API (api.imf.org), SDMX-CSV response.

Page selection. COUNTRY=G001 (World), INDICATOR=AFXRA (Allocated foreign exchange reserves), FXR_CURRENCY in {USD, EUR, JPY, GBP, CNY}, TYPE_OF_TRANSFORMATION in {SHRO_PT (share of allocated reserves, percent), NV_USD (nominal value, USD)}, FREQUENCY=Q. The page filters the stored SHRO_PT (share) rows to these five currencies. The stored data also includes AUD, CAD, CHF, and OTHC; those categories remain outside this view.

Currency-level breakdowns exist only under AFXRA (allocated reserves): the unallocated portion is by construction not decomposed by currency, so a share is always a share of allocated reserves, never of total reserves. COFER individual -country submissions are kept strictly confidential by the IMF, so only aggregate groupings (here, G001 "World") are ever published; there is no country-level COFER to show.

What the page shows, and the exact figures

• Latest-quarter shares (coferLatest()): each currency's SHRO_PT value at the most recent quarter, plus a computed residual = 100 - sum(the five).
• The composition chart (coferShares()): the full quarterly SHRO_PT series for all five currencies, drawn as five lines. The renminbi's line begins at its first reported quarter (2016-Q4), not at zero before then.
• The dollar-share storyline (usdStory(), currencyAnchors()): first, latest, all-time peak and all-time trough of each currency's share, computed by ordering the series. The prose states only what these anchors say; no trend is asserted beyond the numbers.

The five-currency subset limitation (read before quoting a share)

This page selects five currencies from the stored COFER data. Its headline cards, chart, and historical anchors use the same selection. The residual is 100 - sum(the five selected shares), representing the Australian and Canadian dollars, the Swiss franc, and IMF's other-currencies category outside this view. It is not unallocated reserves or missing data. The shares retain their original allocated-reserve denominator; they are not rescaled to sum to 100%.

The full stored series contains all nine reported currency categories. A local check on 2026-09-05 found that their 2026-Q1 shares sum to 100.00% at display precision. The five selected shares sum to 88.99%, leaving 11.01% outside the view. These values are checks on that vintage; the page computes its totals from the current data.

Multi-line, not stacked area

The chart draws five independent lines. Each currency's share can be compared against the others and its own history on a shared scale. The selected currencies are not a full decomposition of allocated reserves.

Revision caveat on recent quarters

COFER is reported voluntarily by IMF member and non-member reporters; recent quarters are provisional until fully reported and revise as late submitters come in. The most recent quarter should be treated as preliminary if used for a headline claim. A cross-check against DBnomics' mirror of COFER (its legacy W00 grouping) matches exactly at 1999-Q1 for all four currencies then reported, with mid-history divergences up to ~2.5pp attributable to G001 and W00 being two independently-revised IMF grouping definitions (documented in data/raw/cofer/SOURCE.md, open item 1). For a precise historical-quarter claim, re-verify that quarter against the live IMF COFER dashboard.

License

IMF data, free to use with attribution: "Source: IMF, Currency Composition of Official Foreign Exchange Reserves (COFER)." No registration or API key required. The confidentiality of individual-country submissions is a structural property of the dataset (only aggregates are published), not a restriction on the World -aggregate data used here.