Our methodology.

Basket spec: the standardized hotel night.

The Rewardopedia Cost Index is one number per destination per month: the Nth percentile of mid-tier hotels-only inventory inside the city's central-area polygon, refreshed on the 1st of each month.

The construct: the typical published room rate at a mid-market chain in the central area. We compute the Nth percentile of the basket samples in USD, with FX snapped on the first of the month.

Currently N is a placeholder (57.5) and is being calibrated against the first 2–3 months of live pipeline data. While N is provisional every figure ships with the Calibrating confidence label.

What's fixed (not calibrated): length of stay = 2 nights; refundable rate; taxes included; USD denomination; first-of-month FX snapshot; hotels-only filter (SerpApi type=Hotel).

What's calibrated post-launch: the percentile slice value, the minimum sample size for Sampled confidence, the number of sample dates, the lead time, and the midweek/weekend mix.

Polygon protocol: inventory-density model.

Each destination has a single fixed central-area polygon. We do not redraw it every month — only when underlying hotel inventory composition shifts materially.

Construction: an unconstrained Google Hotels pull yields a lat/lng cloud. We fit a convex hull around the densest 70% of those points, then subtract a 5 km exclusion zone around any major airport in the destination.

Floor: a polygon must contain ≥ 30 unique hotels after airport exclusion. Below that, the destination renders with Low-sample confidence and a default centroid-plus-1.5km fallback polygon.

Validation: a cross-family LLM judges each polygon against a structured rubric. Any rubric failure or low judge confidence escalates to human review. We also random-audit 5% of approved polygons regardless.

Polygons live as GeoJSON in apps/api/polygon_registry/<slug>.geojson in the repo. Every change goes through PR review.

Sample design: when and what we sample.

Cadence: once per calendar month, executed on the 1st through the Temporal-owned index refresh workflow.

Per destination: a single SerpApi google_hotels call within the polygon, hotels-only, returns a basket of qualifying properties. We compute the Nth percentile of rate_per_night across the basket.

Lead time, length of stay, occupancy: all fixed across destinations to keep the basket comparable. Length of stay is currently 2 nights, refundable rate, taxes included.

Cross-source telemetry was originally planned via Amadeus but dropped from MVP — Amadeus's chain-bias makes naive averaging wrong, and the editorial discipline is stronger than the math gain. We perform quarterly manual audits of 5 random cities instead, archived with dated screenshots.

Confidence labels: a 5-state ladder.

Every measured value on Rewardopedia ships with a confidence chip. The five states, in increasing strength, are:

• ~Low-sample· May 22, 2026Sample below N_min OR polygon below 30-hotel floor OR last sample older than current month.
• ⏱Calibrating· May 22, 2026Methodology v1.0 placeholder period. Backfills to `Sampled` on parameter freeze.
• ⛓Composite· May 22, 2026Derived from multiple inputs of different epistemic states (e.g., trip-cost calculator: measured hotel basket + user daily-spend).
• ✎Editorial· May 22, 2026Judgment calls, not measurements (best card to bring, why this destination is undervalued).
• ✓Sampled· May 22, 2026Current monthly window, sample size ≥ N_min, polygon meets ≥30-hotel floor. The strongest label.

Change log.

Every material methodology change is versioned and documented here. We log the date, what changed, and why — so anyone citing the index knows exactly which methodology produced a given figure.

v1.0 · 2026-05-22

Initial methodology published. Placeholder N=57.5 percentile, N_min=15 sample size, 2-night refundable LOS, USD with FOM FX snap, inventory-density polygons with ≥30-hotel floor and 5km airport exclusion. The first public index run remains pending during the calibration period — every provisional figure ships with the Calibrating confidence label.

Why this index can be trusted.

Anyone can post a price. We publish a standardized, sourced, dated one — and we take no commission on hotel bookings.