Boys' swimming edge over girls grows from age 12

What this chart asks

At what age does the gap between boys' and girls' swimming times open, and how large does it get by 18?

Why it is shown this way

• A line across ages shows when the gap starts to open; ages are evenly spaced whole years, so an ordinal axis is used.
• The y axis starts at zero so the near-zero gap at ages 10-11 is shown honestly.
• The median across 35-53 events per age is plotted so no single stroke or distance drives the line; the dataset lists the minimum and maximum at each age.

Chart annotations

These markers provide relevant context for interpreting the chart. Their timing or position does not, by itself, establish causation.

Gap begins to widen

12

The median gap is under 2% at ages 10-11 and rises every year from 12 to 18.

Data and accessibility

Download chart data · Open accessible table · Download PNG · Download SVG

Dataset sex-gap-sports-performance, analysis swim-age-gap

Sources

This chart draws on the sources of the dataset versions it visualizes.

Male and female athletic performance and physical traits

1. Washington Interscholastic Activities Association (WIAA) Official results of the 2026 State 2A-3A-4A Track and Field Championships, Mount Tahoma Stadium, Tacoma, May 28-30, 2026 (Hy-Tek Meet Manager printout, linked from wiaa.com Track & Field Past Results).

   Retrieved October 10, 2026. Factual results published by WIAA; no license stated. Marks are facts; FactHub republishes places and marks only, without athlete names or schools.

   Archived copy captured October 11, 2026

2. World Athletics Official Paris 2024 athletics results by discipline; each final links to its result page. FactHub checked all 24 winning marks in the paris-winners table (12 events, men and women) against the final result pages on 2026-10-12, and all matched.

   Retrieved October 10, 2026. World Athletics website terms. Marks are facts; linked, not redistributed.

   Archived copy captured October 11, 2026

3. Wikipedia Compiled medal summary for all Paris 2024 athletics events, used to transcribe gold-medal marks.

   Retrieved October 10, 2026. CC BY-SA 4.0. Marks are facts; transcribed values only.

   Archived copy captured October 11, 2026

4. Wikipedia Compiled medal summary for Paris 2024 pool swimming events, used to transcribe gold-medal times.

   Retrieved October 10, 2026. CC BY-SA 4.0. Marks are facts; transcribed values only.

   Archived copy captured October 11, 2026

5. CDC National Center for Health Statistics Fryar CD et al. Anthropometric reference data for children and adults: United States, 2015-2018. Vital Health Stat 3(46), 2021. Mean standing height by sex and age.

   Retrieved October 10, 2026. Public domain (U.S. government work). Unrestricted.

   Archived copy captured October 11, 2026

6. Janssen I, Heymsfield SB, Wang ZM, Ross R (2000) Skeletal muscle mass and distribution in 468 men and women aged 18-88 yr, measured by whole-body MRI. J Appl Physiol 89:81-88.

   Retrieved October 10, 2026. Publisher copyright (American Physiological Society). Values cited from the abstract; not redistributed.

7. Dodds RM et al. (2014) Grip strength across the life course: normative data from twelve British studies (49,964 participants). PLoS One 9:e113637, Table 2.

   Retrieved October 10, 2026. CC BY 4.0. Redistributable with attribution.

   Archived copy captured October 11, 2026

8. CDC National Center for Health Statistics Looker AC et al. Lumbar spine and proximal femur bone mineral density, bone mineral content, and bone area: United States, 2005-2008. Vital Health Stat 11(251), 2012; total femur tables.

   Retrieved October 10, 2026. Public domain (U.S. government work). Unrestricted.

   Archived copy captured October 11, 2026

9. CDC National Center for Health Statistics Hollowell JG et al. Hematological and iron-related analytes: reference data for persons aged 1 year and over, United States, 1988-94. Vital Health Stat 11(247), 2005; Tables 2-3.

   Retrieved October 10, 2026. Public domain (U.S. government work). Unrestricted.

   Archived copy captured October 11, 2026

10. Petersen SE et al. (2017) Reference ranges for cardiac structure and function using cardiovascular magnetic resonance in Caucasians from the UK Biobank (n=804). J Cardiovasc Magn Reson 19:18.

    Retrieved October 10, 2026. CC BY 4.0. Redistributable with attribution.

    Archived copy captured October 11, 2026

11. Kaminsky LA et al. (2015) Reference standards for cardiorespiratory fitness measured with cardiopulmonary exercise testing: data from the FRIEND registry (7,783 U.S. treadmill tests). Mayo Clin Proc 90:1515.

    Retrieved October 10, 2026. Publisher copyright; author manuscript in PMC. Values cited; not redistributed.

    Archived copy captured October 11, 2026

12. Lipps DB, Galecki AT, Ashton-Miller JA (2011) On the implications of a sex difference in the reaction times of sprinters at the Beijing Olympics. PLoS One 6:e26141.

    Retrieved October 10, 2026. CC BY. Redistributable with attribution.

    Archived copy captured October 11, 2026

13. Woods DL et al. (2015) Factors influencing the latency of simple reaction time (1,469 U.S. adults, precisely timed hardware). Front Hum Neurosci 9:131. Reports simple reaction time unaffected by sex.

    Retrieved October 10, 2026. CC BY 4.0. Redistributable with attribution.

    Archived copy captured October 11, 2026

14. Washington Interscholastic Activities Association (WIAA) Official results of the 2022 State 2A-3A-4A Track and Field Championships.

    Retrieved October 12, 2026. Factual results published by WIAA; no license stated. Marks are facts; FactHub republishes places and marks only, without athlete names or schools.

    Archived copy captured October 12, 2026

15. Washington Interscholastic Activities Association (WIAA) Official results of the 2023 State 2A-3A-4A Track and Field Championships.

    Retrieved October 12, 2026. Factual results published by WIAA; no license stated. Marks are facts; FactHub republishes places and marks only, without athlete names or schools.

    Archived copy captured October 12, 2026

16. Washington Interscholastic Activities Association (WIAA) Official results of the 2024 State 2A-3A-4A Track and Field Championships.

    Retrieved October 12, 2026. Factual results published by WIAA; no license stated. Marks are facts; FactHub republishes places and marks only, without athlete names or schools.

    Archived copy captured October 12, 2026

17. Washington Interscholastic Activities Association (WIAA) Official results of the 2025 State 2A-3A-4A Track and Field Championships.

    Retrieved October 12, 2026. Factual results published by WIAA; no license stated. Marks are facts; FactHub republishes places and marks only, without athlete names or schools.

    Archived copy captured October 12, 2026

18. World Aquatics Official results service of the swimming governing body: the Paris 2024 event list, from which each final's result is read at /fina/events/{id}. FactHub checked all 16 swimming winning times in the paris-winners table against it on 2026-10-12, and all matched.

    Retrieved October 12, 2026. World Aquatics website terms. Marks are facts; linked, not redistributed.

    Archived copy captured October 12, 2026

19. USA Swimming USA Swimming 2024-2028 Single Age Motivational Standards: time standards (B to AAAA) for girls and boys at each age from 10 to 18, in every event and course; linked from usaswimming.org/times/time-standards.

    Retrieved October 12, 2026. USA Swimming publication; no license stated. Time standards are factual cut times; FactHub republishes the times with its computed gap.

    Archived copy captured October 12, 2026

20. Wikipedia Compiled list of outdoor U.S. high-school national records with athlete, school, meet and date, citing meet results and news reports.

    Retrieved October 12, 2026. CC BY-SA 4.0. Marks are facts; transcribed values only.

    Archived copy captured October 12, 2026

Limitations

• Time standards describe strong age-group swimmers (the AAAA level), not all children.
• USA Swimming does not describe its method in the standards document; secondary sources say the standards are based on recent national 16th-place times.
• Ten-year-olds have fewer events (35) than older ages (51-53).