Data quality updated: 2026-09-15 09:13 UTC
WTA Data Quality & Coverage
Coverage, update times, sources, and known gaps in the WTA statistics.
How to read this page
Check which WTA matches and seasons are covered, when the data was updated, and where gaps remain. The source notes explain how records are combined and why a statistic may differ from another reference.
Counts cover recorded completed main-tour and Olympic singles matches. They describe the size of the archive, not the percentage of all historical matches captured.
Coverage Overview
Data Sources
| Source | Period | Matches | Share |
|---|---|---|---|
| Jeff Sackmann / Tennis Abstract (opens in new tab) | 1968–2024 | 140,117 | 89.9% |
| BALLDONTLIE API | Historical match gap-fill and 2025–present live and current data | 14,996 | 9.6% |
| International Tennis Federation (opens in new tab) | Official Olympic singles draws, 1988–present | 622 | 0.4% |
| Manual corrections & other reconciled sources | Rows retained after source review | 109 | 0.1% |
Source Priority Rules
Which source is used when records overlap or disagree.
Matches
Historical WTA matches can use both Jeff Sackmann and BALLDONTLIE records. Records for the same match are combined, with BALLDONTLIE used to fill gaps or resolve player and tournament identity conflicts.
Rankings
WTA rankings use Sackmann snapshots before 2025 and BALLDONTLIE snapshots from 2025 onward. Sackmann provides the more extensive historical archive. Official WTA snapshots can supplement incomplete current coverage.
Categories
Historical categories use documented modern equivalents for comparisons. A tournament's current category is not automatically applied to every past edition.
Olympic singles
Official ITF draws supply the complete medal-era singles archive from Seoul 1988 through the latest completed Games. Gold counts as one title; event-time NOCs remain distinct from current nationality. Walkovers count in TennisDB W-L records and streaks but do not affect Elo or played-only stats.
Coverage by Era
WTA main-tour singles match records by decade. Coverage improves in more recent decades as data sources become more comprehensive.
| Decade | Matches |
|---|---|
| 1960s | 5,808 |
| 1970s | 24,386 |
| 1980s | 27,164 |
| 1990s | 23,377 |
| 2000s | 24,699 |
| 2010s | 28,415 |
| 2020s | 21,995 |
Advanced Metric Coverage
Advanced metrics stay blank when the required evidence is unavailable. Leaderboards apply additional minimum-sample and point-stat coverage rules.
| Metric family | Available evidence |
|---|---|
| Elo, surface lift, and schedule effect | All eras with eligible match results and opponent identities. |
| Performance+, Set Win %, Set Margin, deciding sets, and tiebreaks | Matches with parseable completed scores; older seasons may have gaps. |
| Serve+, Return+, Point Dominance, and Total Points Won % | Matches with usable serve and return statistics. Values are best-effort, match-weighted, and shrunk toward the tour-season baseline because historical sources do not always expose point denominators. |
Data Freshness
When site data was last updated.
| Event | Time (UTC) | Status |
|---|---|---|
| Last data ingest | Sep 15, 2026 9:16 UTC | success |
| Last serving layer refresh | Sep 15, 2026 9:13 UTC | success |
Known Limitations
Accepted data limitations that we are aware of and working to improve over time.
Historical match coverage varies by era
TennisDB's open historical WTA record is broad, but it is not an official completeness census. Coverage varies by event, era, round, and available source, so older win-loss records and title counts can be lower than WTA official figures. The decade counts above describe what TennisDB currently holds; they are not completeness percentages.
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 and 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.
Historical tournament categories use modern equivalents
TennisDB groups documented historical predecessor editions—including Tier I-V and Premier-era classifications—under modern WTA 1000, WTA 500, and WTA 250 categories for cross-era comparison. Historical labels remain separate in the audit record, and editions without a supported mapping retain their recorded category.
Detailed performance-stat coverage is partial
Serve and return metrics are calculated only when a match has the core detailed-stat inputs needed by every displayed percentage. Player, season, and head-to-head pages expose detailed-stat matches over total main-draw matches so partial samples are visible rather than presented as complete.
"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.
Weekly WTA ranking coverage begins in 1984
The official WTA singles computer ranking began on 3 November 1975, but TennisDB's available weekly snapshots begin in 1984; the missing snapshots remain a source-coverage gap. Audited official No. 1 change dates and year-end Top 10 ranks cover the highest-value facts from 1975 onward without being presented as a complete weekly history. WTA doubles rankings began in 1984.
Recently retired players on active leaderboards
Players who have retired but still hold an WTA ranking (within the 52-week rolling window) may appear on active leaderboards until their ranking points expire naturally.
If you spot something that looks wrong, please let us know.