CUE Research · Study 2
NHL Players and Their Birthdays
All 850 players on 2024-25 NHL rosters: one of the best-documented birthday anomalies in the world.
The question: Are elite hockey players born at random times of year?
What stands out
- Clear difference · Birth quarter
All players: Jan–Mar appears 281 times against about 210.0 expected (1.34×).
- Clear difference · Birth quarter
Canadian-born: Oct–Dec appears only 52 times against about 85.6 expected.
- Clear difference · Birth quarter
Canadian-born: Jan–Mar appears 116 times against about 84.0 expected (1.38×).
- Clear difference · Birth quarter
U.S.-born: Jan–Mar appears 91 times against about 64.0 expected (1.42×).
- Clear difference · Birth month
All players: Jan appears 102 times against about 72.1 expected (1.41×).
- Clear difference · Birth month
Canadian-born: Feb appears 44 times against about 26.3 expected (1.67×).
- Clear difference · Birth quarter
All players: Oct–Dec appears only 169 times against about 214.1 expected.
Worth watching, not enough to claim
- Sun sign
All players: Aquarius appears 95 times against about 69.8 expected (1.36×).
- Sun sign
Canadian-born: Taurus appears 45 times against about 28.9 expected (1.56×).
- Birth month
U.S.-born: Jan appears 36 times against about 22.0 expected (1.64×).
- Birth month
All players: Feb appears 90 times against about 65.8 expected (1.37×).
- Birth month
Canadian-born: May appears 44 times against about 28.9 expected (1.52×).
- Sun sign
All players: Libra appears only 47 times against about 69.8 expected.
All players: Jan–Mar appears 281 times against about 210.0 expected. That is a clear difference for a group of 850.
Context What explains it
No. Researchers have found the same pattern for decades: players are born disproportionately early in the year. It is called the relative age effect.
Youth hockey groups children by calendar year, so a child born in January can be almost a year older than a teammate born in December. Older children tend to be bigger and more developed, get picked for stronger teams, receive more coaching and ice time, and the advantage compounds.
The sun-sign pattern follows from the birth-month one: Capricorn, Aquarius and Pisces are winter signs. It is a real pattern in the stars CUE reads, with an ordinary cause, and a good reminder to look for the simplest explanation first.
The baseline assumes births are spread evenly through the year. In reality slightly more babies are born in spring and summer, which makes the early-year excess here, if anything, more striking.
Source The data
- NHL official rosters, 2024-25 season. Retrieved 2026-09-27. View source
- Every player listed on the 32 teams’ 2024-25 rosters in the NHL’s public API, with birth dates and countries as the league publishes them.
- Verification: 850 of 850 included. Official league records: birth dates as the NHL publishes them.
- Expected values: every day of the years each group was born in, weighted by how many people were born in each year, run through CUE’s engine. Weighting matters for Chinese signs and Life Paths, which depend on the year.
- A difference is called clear only in groups of 50 or more and at least three standard errors from expected. Because each study tests about a hundred values, a clear difference needs 3.5 standard errors; 2.5 to 3.5 is only “worth watching”.
Reproduce it: the raw data snapshots and build scripts are in CUE’s code repository (scripts/data and scripts/build-*-study.mts).
Further reading
- Barnsley, Thompson & Barnsley, “Hockey success and birthdate: the relative age effect”, Canadian Association for Health, Physical Education and Recreation Journal 51 (1985)
- Cobley, Baker, Wattie & McKenna, “Annual age-grouping and athlete development: a meta-analytical review of relative age effects in sport”, Sports Medicine 39 (2009)
- Gladwell, Outliers (Little, Brown, 2008), chapter 1