Wikipedia Importance Scores

Place importance scores derived from Wikipedia link count, replacing raw population as the FST emission prior weight. Shipped in #173.

Source

Nominatim's wikimedia-importance.csv.gz — 19M rows mapping Wikidata IDs to importance scores. The score is log(total_links) / log(max_links) where total_links = internal links + cross-language links to the Wikipedia article. Normalized to [0, 1] where the United States article (5.2M links) = 1.0.

ETL pipeline

wikimedia-importance.csv.gz (19M rows, ~250 MB compressed)
         │
         ▼
  scripts/build-importance.ts
         │
         ├─ Load WOF concordances (other_source='wd:id') → Set of needed Wikidata IDs
         ├─ Stream-decompress TSV, filter to matching IDs only
         ├─ Collapse duplicates by MAX(importance) per Wikidata ID
         ├─ JOIN: wof_id → concordance wikidata_id → importance score
         ├─ Write place_importance(id, importance) table
         └─ Population fallback: min(1.0, log2(1+pop/1000)/14) for places without Wikidata

Coverage (US admin)

Source	Places
Wikipedia importance (via Wikidata concordance)	47,348
Population fallback	108,111
Total in place_importance	155,459

How scores flow into the FST

1. build-importance.ts writes place_importance table into the WOF SQLite
2. fst-builder.ts reads place_importance (falls back to place_population → pseudo-importance)
3. PlaceEntry.importance carries the score through serialization (Float32 in the binary FST)
4. fst-prior.ts computes bias: importance × biasScale × maxBias (linear, capped at 3.0 logits)

Why not population

Signal	Washington DC	Washington state	Winner
Population	678K	7.6M	State (wrong for bare "Washington")
Wikipedia importance	0.815	0.764	DC (correct — more culturally prominent)

Population is an administrative headcount. Wikipedia importance captures actual cultural prominence — how often the place is referenced, linked to, and discussed across languages.

Regeneration

Run after any WOF data refresh:

node scripts/build-importance.js --db /path/to/wof-unified.db [--tsv /path/to/wikimedia-importance.csv.gz]

The TSV is cached at /tmp/wikimedia-importance.csv.gz after first download. Pass --tsv to skip the download.

See also

• FST Gazetteer LM — the FST architecture this feeds into
• Nominatim importance docs — upstream methodology