Anchored parameters

Coefficient sets, reading defaults and versioning

A coefficient set is everything the anchored rule learns, frozen and named. The rule itself never changes; only the set it reads does:

\[ \hat s=a+b_\Delta\,\Delta+b_r\,r,\qquad \hat y=c\,(1+\hat s). \]

Symbols follow the notation page; the anchored family explains each term.

Coefficient sets

Each column is one shipped AnchoringParameters. The first three rows are the rule’s coefficients; the rest are the limits the eligibility gate enforces and the set’s identity.

Field	Symbol	anchoring-2025-01	core-2025-01
customary_beat	\(a\)	0.0112	0.0089
gap_weight	\(b_\Delta\)	0.1290	0.0442
revision_weight	\(b_r\)	1.2800	1.2348
maximum_absolute_gap		25%	25%
maximum_prediction_age		21 days	21 days
maximum_consensus_age		60 days	60 days
fitted_through		2024-12-31	2024-12-31

• ANCHORING_2025_01: The default set.
• CORE_2025_01: The core-model coefficients, with a smaller gap weight \(b_\Delta\).
• Same window: Both sets were fitted through the same date, so a choice between them is a choice of model, not of period.

Prior work records where the numbers came from.

Versioning

• A new set is a new version: A changed coefficient or limit needs a new version. A shipped set is never edited in place.
• Every row names its set: parameters_version on each published row ties \(\hat s\) to the \(a\), \(b_\Delta\) and \(b_r\) that produced it.
• Training window: Publication requires fitted_through to precede the reading date; an earlier as_of raises PanelError.
• Loading: Use AnchoringParameters.model_validate(payload) for an application’s own set. Unknown fields fail rather than being ignored.

Reading defaults

The revision \(r=c/c_{-30}-1\) compares two consensus reads. These defaults set how far apart they are and how old each may be; they belong to the reading policy, not to a coefficient set.

Setting	Default	Role
lookback	30 days	Gap between \(c\) and \(c_{-30}\)
maximum_revision_age	60 days	Oldest either consensus read may be for \(r\)

• Publication: publish_anchored uses these defaults.
• Custom preparation: Pass lookback= and maximum_revision_age= to prepare_anchored_subjects.
• Missing revision: A missing \(c_{-30}\) drops the \(b_r\,r\) term; it does not refuse the subject.

Renamed constants

• ANCHORING_2025_01: Replaces STUDY_2025_01 for new code.
• Compatibility: The old name warns but preserves its object and version for replay.