Evaluating Pegs

Pegs Policy

The bar for entries in db/seeds/pegs/. These definitions directly affect blend calculations, and this skill defines what qualifies and what doesn't.

The Bar

A currency belongs in db/seeds/pegs/ only if all of the following are true:

1. Officially asserted by an issuing authority (central bank, monetary authority, currency board, or government).
2. Currently in force — not historical. If a peg ended, remove the entry; don't keep it with a sunset date.
3. A specific rate is asserted, not a band, target, or "managed float."
4. A primary source exists: the issuing authority's own page, a treaty, or legislation. Wikipedia is acceptable as a fallback for long-standing colonial / dependency pegs (FKP, SHP, GGP, IMP, JEP, BMD, BTN, MOP, CVE, ANG, QAR, OMR) where the authority doesn't publish a dedicated peg page, but a central-bank URL is preferred whenever available.

If any one of these fails, the currency does not belong in the file.

What Does Not Qualify

• De facto pegs: stable in practice but never officially declared. Example: AZN/USD has been flat at 1.7 since May 2017, but CBAR has not asserted a peg. Adding it makes us responsible if it breaks.
• Crawling pegs / managed floats: the rate moves within a band (e.g., CNY) or is "managed" without a fixed target.
• Currency boards with derived rates: if the rate is mechanically derived from another (e.g., dollarization), the currency is its base — no peg row needed unless there's a non-1 multiplier.
• Historical pegs: if a peg has ended, it does not belong here. Look up the current regime.
• Forecasts or expectations: "expected to peg" or "will likely peg." Wait until it's official.

Schema

Each entry in db/seeds/pegs/:

{
  "quote": "AED",
  "base": "USD",
  "rate": 3.6725,
  "since": "1997-11-02",
  "authority": "Central Bank of the UAE",
  "source": "https://www.centralbank.ae/en/our-operations/currency-operations/exchange-rates"
}

All six fields are required (enforced by Peg = Data.define(...) in lib/peg.rb):

• quote — the pegged currency (ISO 4217)
• base — what it's pegged to (ISO 4217)
• rate — 1 base = rate quote. Default 1.0 for parity pegs.
• since — date the current peg took effect, ISO 8601. Used to suppress peg-derived rates before this date.
• authority — the human-readable name of the asserting body.
• source — a stable URL. Central-bank page preferred; Wikipedia acceptable for long-standing dependency pegs.

Adding an Entry

1. Find the primary source. Search the central bank or monetary authority's website. Look for "exchange rate policy," "monetary policy," or "currency arrangement." If only Wikipedia turns up something, check whether the bank's own site mentions it elsewhere — sometimes the peg is buried under a different title.
2. Confirm the rate is current. Some pages cite historical rates that have since been revised (e.g., Saudi riyal has had multiple regimes; the current peg dates to 1986). Match since to the current peg, not the original one.
3. Add to db/seeds/pegs/ as <quote>.json (lowercase, e.g. aed.json).
4. No code changes needed — Peg.all auto-discovers files in the directory.
5. Add a test case to spec/peg_spec.rb if the entry has unusual structure (non-1 rate, non-USD base, etc.) — for parity USD pegs, the existing tests cover it.

Removing an Entry

If a peg is officially abandoned (e.g., 2015 CHF/EUR style), remove the entry. Do not leave it with an until field — the schema doesn't support one and the rate becomes wrong the moment the peg breaks.

If you discover an entry that doesn't meet the bar (a de facto peg slipped in), remove it.