# WTA Data Quality & Coverage

Source: https://tennis-db.com/wta/data-quality
Tour: WTA

## Coverage overview
- Total matches: 164755
- Players: 6630
- Tournaments: 4661
- Tournament editions: 6857
- Earliest match date: 1967-12-25
- Latest match date: 2026-07-23
- Sackmann matches: 141187
- BallDontLie matches: 23481

## Source priority rules
- Matches: Jeff Sackmann and BallDontLie rows can both be eligible across historical WTA seasons. The refresh pipeline deduplicates equivalent matches and keeps BallDontLie rows when they fill coverage gaps or carry the better reconciled identity.
- Rankings: WTA rankings use Sackmann snapshots before 2025 and BallDontLie snapshots from 2025 onward. That strict split is intentional because Sackmann's historical WTA ranking coverage is denser than BallDontLie's.
- Categories: Tournament categories are normalized during ingest and stored in the serving layer, so pages use one canonical category value instead of reinterpreting source-specific codes at request time.

## Coverage by era
| Decade | Matches |
| ---: | ---: |
| 1960s | 5975 |
| 1970s | 24971 |
| 1980s | 27544 |
| 1990s | 23248 |
| 2000s | 24507 |
| 2010s | 29342 |
| 2020s | 29168 |

## Data freshness
- Last data ingest:  (-)
- Last serving layer refresh: 2026-07-23 (success)

## Known limitations
- Historical match coverage varies by era: The Sackmann dataset is the most comprehensive open WTA dataset, but does not cover 100% of historical matches. Coverage is approximately 95% for the 2000s, 90% for the 1990s, 85% for the 1980s, and 80% for the 1970s. Win-loss records and title counts for older players may be slightly lower than WTA official figures.
- WTA match sources are reconciled across eras: WTA match pages use Jeff Sackmann's data where it is available and BallDontLie rows as historical gap-fill as well as live/current coverage. Equivalent rows are deduplicated during refresh, so BallDontLie can appear before 2025 on WTA match-driven pages when it fills a known coverage gap.
- WTA rankings use the denser historical source: WTA ranking pages use Sackmann rankings before 2025 and BallDontLie rankings from 2025 onward. This differs from WTA matches because Sackmann's historical ranking snapshots are strong even where historical match coverage is incomplete.
- Pre-2009 tournament categories are approximate: Modern category labels (WTA 250, WTA 500) are applied retroactively to pre-2009 events. Historical tier distinctions are not preserved because no upstream data source provides them.
- "Turned pro" year is approximate for historical players: For players active before ~2000, the displayed turned-pro year reflects the first season with WTA main-tour match data, which may differ from official records by 1-3 years.
- Prize money is source-dependent: Career prize money is reconciled from official tour PDFs, Wikidata, and BallDontLie where available. Most prominent historical players should have values, but lower-ranked historical players may still have gaps.
- Rankings before 1984 do not exist: The WTA computer ranking system began in 1984. No rankings are available for earlier seasons.
- Recently retired players on active leaderboards: Players who have retired but still hold a WTA ranking (within the 52-week rolling window) may appear on active leaderboards until their ranking points expire naturally.

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Canonical URL: https://tennis-db.com/wta/data-quality
Data source: TennisDB (tennis-db.com)