CUE Research · Study 14

Chess Grandmasters

More than two thousand holders of chess’s highest title.

The question: Do the world’s strongest chess players share numbers, signs or birthdays?

What stands out

  • Clear difference · Birth month

    Born since 1950: Jan appears 211 times against about 161.8 expected (1.30×).

  • Clear difference · Birth month

    All grandmasters: Jan appears 228 times against about 178.2 expected (1.28×).

  • Clear difference · Chinese sign

    Born before 1950: Ox appears 31 times against about 16.2 expected (1.92×).

  • Clear difference · Chinese sign

    Born before 1950: Pig appears 31 times against about 16.2 expected (1.91×).

  • Clear difference · Birth quarter

    All grandmasters: Oct–Dec appears only 455 times against about 528.7 expected.

Worth watching, not enough to claim

  • Birth quarter

    Born since 1950: Oct–Dec appears only 414 times against about 480.1 expected.

  • Birth quarter

    All grandmasters: Jan–Mar appears 587 times against about 518.6 expected (1.13×).

  • Chinese sign

    Born before 1950: Cat appears only 3 times against about 15.7 expected.

  • Birth month

    All grandmasters: Dec appears only 137 times against about 178.2 expected.

  • Birth quarter

    Born since 1950: Jan–Mar appears 527 times against about 470.9 expected (1.12×).

  • Day energy + Life Path

    All grandmasters: 1 day · LP 9 appears 47 times against about 30.8 expected (1.52×).

All grandmasters: Oct–Dec appears 455 times against about 528.7 expected. That is a clear difference for a group of 2099.

All grandmasters Expected, random birthdays 1865–2013 Clear difference Worth watching

Context What explains it

Junior chess events are often grouped by calendar-year age, so a small relative age effect is possible, as found in some studies of young players. The study looks for it in the birth-quarter view.

The Grandmaster title is awarded on results, so it means the same thing in every country.

Source The data

  • Chess grandmasters. Retrieved 2026-09-28. View source
  • Every person Wikidata records as holding FIDE’s Grandmaster title, the highest title in chess, awarded for results against strong opposition.
  • Verification: 2099 of 2128 included. A person is included when Wikidata records one birth date at day precision.
  • 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

  • FIDE title regulations
  • Wikidata, chess title records