Performance thresholds, efficiency, and access equity in junior girls' tennis: longitudinal analysis and bayesian...

Percentile-based thresholds in the International Tennis Federation (ITF) junior ranking system are widely used to gauge competitive standing, yet little is known about their long-term dynamics, systemic biases, and predictive validity. Total Ranking Points (TRP) reflect cumulative achievement but are affected by tournament volume and access. Points per Event (PPE) have therefore been proposed as a complementary efficiency-based metric. The age at which thresholds are reached and the geographic distribution of top performers are critical for understanding developmental timing and equity of access.

This study aimed to (1) quantify and forecast cut-off thresholds (P₉₀, P₇₅, P₅₀) categories using TRP and PPE; (2) examine the age of players achieving these benchmarks; (3) assess geographic representation at P₉₀; and (4) test whether trajectories display linear stability or accelerating progression.

A longitudinal dataset of 8,413 junior female players ranked in ITF year-end lists (2004-2024) was analysed. TRP were obtained from ITF records, while PPE were calculated as TRP divided by sanctioned tournament entries. Annual percentile cut-offs were derived using binary logistic regression. Geographic equity was assessed via country counts, Shannon diversity, and a sensitivity criterion (≥ 2 players per country). Player ages were calculated from birth year and tested with regression and Kendall's τ. Bayesian Prophet models forecast 2025-2029 thresholds, configured for changepoint detection.

TRP thresholds rose exponentially, while PPE trajectories were more variable. P₉₀ age remained stable at 16 years, whereas P₇₅ and P₅₀ trended older. Geographic access at P₉₀ was stable but concentrated, with only 5-10 countries represented annually and repeated multi-player presence limited to a few nations (e.g., USA, Russia, Czechia). Forecasts indicated TRP cut-offs will continue to rise through 2029, with P₉₀ exceeding 1,400 points, while PPE trends remained less stable.

The ITF junior girls' ranking system shows accelerating cumulative thresholds (TRP) alongside less predictable efficiency-based patterns (PPE). Elite entry age remains consistently young, broader tiers are ageing, and access to P₉₀ is dominated by a small group of nations. Percentile thresholds therefore capture systemic competitiveness more than intrinsic ability, offering valuable but context-dependent insights for planning and equity in talent development.