How Hockey ChangedBodies
The Share of Canadian NHLers Born January to June Rose From 42% in 1960-61 to 64% Last Season
Canadians born before 1950 were spread evenly across the calendar. The early-birthday edge Malcolm Gladwell made famous arrived with Gretzky’s generation, and it fades among the players who last.
By Edgehalla ResearchPublished 7 min read
On June 9, 1984, at the Montreal Forum, the Pittsburgh Penguins drafted Mario Lemieux first overall. Unhappy with the contract talks, he wouldn’t pull on their sweater. In the third round the Canadiens took a Quebec City goalie, Patrick Roy. The two were born on the same day, Oct. 5, 1965. In 1984 a Quebec study found fewer than one boy in ten on the province’s top teams for 11- and 12-year-olds, the Pee Wee AA class, with a birthday that late in the year. That same year, Paula Barnsley noticed odd birthdates on Canadian junior rosters. When she and Roger Barnsley, a psychologist, counted the NHL, three in five players were born in the first half of the year.
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For Canadians born before 1950, a birthday meant nothing
The Barnsleys were counting the league of 1982-83. Go back a generation and their pattern vanishes. Canadians born before 1950 had no January edge at all.
In 1960-61, the most common birth month among Canadian NHLers was December, with 23 players. Six of them are in the Hall of Fame as players: Doug Harvey, Terry Sawchuk, Alex Delvecchio, Norm Ullman, Pierre Pilote and Harry Howell. More were born October to December (49) than January to March (40).
Over the whole era it evens out. Of the 1,750 Canadians born from 1880 to 1949 who played an NHL game, 49.9% were born January to June, almost exactly half. Each three-month stretch of the year held about a quarter of them: 26% January to March, 25% October to December.
The chart below sorts players by the five years they were born in (the 1955 point is everyone born 1955-59) and counts each player once. Watch the Canadian line hover around the even-spread mark until the 1950s, then jump.
The lean toward early birthdays starts with players born in the 1950s
Share born January to June, by five-year birth group (each player counted once)
Show data
| Year | Canada | Canada (range) | United States | Europe |
|---|---|---|---|---|
| 1890 | 56.1% | 43.3% to 68.2% | – | – |
| 1895 | 55.7% | 44.7% to 66.1% | – | – |
| 1900 | 51.5% | 41.7% to 61.2% | – | – |
| 1905 | 55.9% | 47.2% to 64.2% | – | – |
| 1910 | 53.4% | 44.9% to 61.6% | – | – |
| 1915 | 50.7% | 42.7% to 58.6% | – | – |
| 1920 | 52.4% | 44.3% to 60.5% | – | – |
| 1925 | 49.7% | 42.2% to 57.2% | – | – |
| 1930 | 47.9% | 40.5% to 55.4% | – | – |
| 1935 | 49.0% | 41.1% to 56.9% | – | – |
| 1940 | 43.9% | 36.5% to 51.6% | – | – |
| 1945 | 46.4% | 40.7% to 52.1% | – | – |
| 1950 | 49.7% | 44.6% to 54.9% | 56.0% | 58.3% |
| 1955 | 57.9% | 52.9% to 62.6% | 56.0% | 53.8% |
| 1960 | 63.6% | 58.9% to 68.0% | 60.4% | 58.1% |
| 1965 | 62.6% | 58.2% to 66.8% | 55.6% | 52.2% |
| 1970 | 60.1% | 54.8% to 65.1% | 53.8% | 57.7% |
| 1975 | 59.0% | 53.8% to 64.0% | 57.8% | 59.6% |
| 1980 | 59.1% | 53.8% to 64.2% | 57.1% | 58.9% |
| 1985 | 58.8% | 53.5% to 63.9% | 59.2% | 58.4% |
| 1990 | 66.1% | 60.8% to 71.1% | 57.3% | 51.3% |
| 1995 | 60.8% | 54.9% to 66.4% | 58.2% | 55.7% |
- 1951: Addona & Yates: effect begins
- Reference: Even spread (49.6%)
Early birthdays climb with players born in the 1950s: 50% for those born 1950-54, 58% for 1955-59, and about three in five ever since. Others got there first. In 2010 two researchers, Addona and Yates, went through every NHL player to that point and dated the start to Canadians born since 1951. Our count puts it a couple of years later. Taken one birth year at a time, no year from 1940 to 1952 had more than half its Canadian NHLers born January to June. From 1953 through 1970, every year topped 53%. With only 30 to 100 Canadians in each birth year, that turning point could be off by a year or two.
The January kids reached the NHL with Gretzky’s generation
A boy born in 1955 didn’t reach the NHL until the mid-1970s, so the league took about 20 years to show the change. Mark Messier was born on Jan. 18, 1961, and Wayne Gretzky eight days later. Two January boys, born just as the lean took hold.
You can watch it arrive season by season. In 1954-55, fewer than half of Canadian NHLers had January-June birthdays. It stayed that way for 23 seasons and hit bottom at 40% in 1961-62. In 1977-78 it reached half again. Five seasons later it was 60%.
That 1982-83 season was the one the Barnsleys counted: 715 players, 61.8% born January to June. On the Oilers, Dave Hunter was born on New Year’s Day, and 18 of the 29 who played that season had first-half birthdays.
Canadian NHLers swung to early birthdays in the late 1970s and never swung back
Share of NHL players born January to June. Each player who played that regular season counts once, by birth country
Show data
| Season | Canada | United States | Europe |
|---|---|---|---|
| 1926-27 | 46.8% | – | – |
| 1927-28 | 51.1% | – | – |
| 1928-29 | 48.9% | – | – |
| 1929-30 | 47.9% | – | – |
| 1930-31 | 54.4% | – | – |
| 1931-32 | 55.2% | – | – |
| 1932-33 | 58.0% | – | – |
| 1933-34 | 53.0% | – | – |
| 1934-35 | 55.5% | – | – |
| 1935-36 | 56.5% | – | – |
| 1936-37 | 55.3% | – | – |
| 1937-38 | 59.7% | – | – |
| 1938-39 | 60.4% | – | – |
| 1939-40 | 57.1% | – | – |
| 1940-41 | 61.6% | – | – |
| 1941-42 | 57.1% | – | – |
| 1942-43 | 51.9% | – | – |
| 1943-44 | 50.4% | – | – |
| 1944-45 | 50.4% | – | – |
| 1945-46 | 57.6% | – | – |
| 1946-47 | 60.0% | – | – |
| 1947-48 | 52.2% | – | – |
| 1948-49 | 52.3% | – | – |
| 1949-50 | 51.3% | – | – |
| 1950-51 | 51.0% | – | – |
| 1951-52 | 49.7% | – | – |
| 1952-53 | 50.3% | – | – |
| 1953-54 | 50.0% | – | – |
| 1954-55 | 49.7% | – | – |
| 1955-56 | 48.6% | – | – |
| 1956-57 | 46.5% | – | – |
| 1957-58 | 40.8% | – | – |
| 1958-59 | 43.5% | – | – |
| 1959-60 | 41.9% | – | – |
| 1960-61 | 42.1% | – | – |
| 1961-62 | 40.0% | – | – |
| 1962-63 | 42.8% | – | – |
| 1963-64 | 40.6% | – | – |
| 1964-65 | 41.9% | – | – |
| 1965-66 | 41.1% | – | – |
| 1966-67 | 41.8% | – | – |
| 1967-68 | 44.6% | – | – |
| 1968-69 | 44.7% | – | – |
| 1969-70 | 45.7% | – | – |
| 1970-71 | 45.2% | – | – |
| 1971-72 | 45.9% | – | – |
| 1972-73 | 48.9% | – | – |
| 1973-74 | 48.8% | – | – |
| 1974-75 | 48.6% | – | – |
| 1975-76 | 49.0% | – | – |
| 1976-77 | 49.1% | – | – |
| 1977-78 | 50.3% | – | – |
| 1978-79 | 51.2% | – | – |
| 1979-80 | 54.8% | 64.1% | – |
| 1980-81 | 57.7% | 60.6% | – |
| 1981-82 | 58.9% | 57.7% | 56.1% |
| 1982-83 | 60.0% | 65.6% | 59.7% |
| 1983-84 | 60.0% | 68.7% | 51.8% |
| 1984-85 | 60.1% | 62.6% | 54.4% |
| 1985-86 | 60.0% | 62.5% | 57.6% |
| 1986-87 | 60.7% | 57.6% | 62.1% |
| 1987-88 | 59.7% | 58.9% | 59.6% |
| 1988-89 | 60.4% | 54.5% | 55.2% |
| 1989-90 | 62.3% | 53.4% | 56.5% |
| 1990-91 | 61.9% | 57.0% | 59.5% |
| 1991-92 | 62.2% | 55.2% | 60.9% |
| 1992-93 | 62.5% | 61.7% | 56.9% |
| 1993-94 | 61.9% | 59.9% | 57.3% |
| 1994-95 | 59.7% | 56.8% | 61.4% |
| 1995-96 | 59.5% | 58.3% | 63.3% |
| 1996-97 | 59.5% | 56.4% | 60.0% |
| 1997-98 | 59.0% | 54.4% | 61.9% |
| 1998-99 | 59.3% | 58.5% | 59.6% |
| 1999-00 | 57.8% | 54.8% | 61.4% |
| 2000-01 | 57.7% | 55.4% | 57.4% |
| 2001-02 | 58.2% | 57.1% | 57.2% |
| 2002-03 | 59.2% | 58.6% | 55.8% |
| 2003-04 | 57.1% | 56.9% | 58.0% |
| 2004-05 | – | – | – |
| 2005-06 | 58.8% | 59.3% | 57.0% |
| 2006-07 | 57.5% | 56.9% | 54.1% |
| 2007-08 | 55.9% | 58.4% | 54.5% |
| 2008-09 | 56.2% | 59.3% | 55.4% |
| 2009-10 | 55.2% | 58.0% | 56.4% |
| 2010-11 | 55.4% | 57.2% | 55.0% |
| 2011-12 | 56.2% | 56.5% | 57.1% |
| 2012-13 | 58.3% | 55.6% | 56.3% |
| 2013-14 | 60.5% | 55.8% | 53.5% |
| 2014-15 | 60.7% | 52.1% | 53.6% |
| 2015-16 | 59.1% | 53.7% | 53.5% |
| 2016-17 | 59.1% | 53.4% | 50.4% |
| 2017-18 | 60.6% | 53.1% | 51.5% |
| 2018-19 | 61.4% | 52.9% | 52.9% |
| 2019-20 | 59.9% | 57.1% | 51.7% |
| 2020-21 | 58.7% | 56.7% | 54.1% |
| 2021-22 | 59.7% | 57.4% | 54.5% |
| 2022-23 | 59.4% | 57.8% | 55.6% |
| 2023-24 | 61.5% | 56.3% | 53.3% |
| 2024-25 | 61.3% | 57.8% | 53.7% |
| 2025-26 | 64.2% | 55.0% | 52.7% |
- 1982-83: Barnsleys count 715 NHLers
- Reference: Even spread (49.6%)
The Canadian line sags below the even-spread mark through the 1960s, crosses it in the late 1970s and has sat near three in five ever since. The usual explanation is the cutoff date. Today minor hockey groups children by calendar year of birth, so a boy born in January plays against boys up to a year younger. He looks more talented and gets picked for the better teams. Malcolm Gladwell’s Outliers, which opens at junior hockey’s 2007 Memorial Cup in Vancouver, made the idea famous in 2008. The 1950s turn fits that explanation. We could not find a reliable date for when Canadian minor hockey settled on calendar-year groups, though, so we can’t tie the turn to a rule change.
Now February outnumbers November nearly three to one
Nearly 50 years after the line crossed half, the lean is plainest on a calendar. Last season, 53 Canadian NHLers were born in February and 51 in January. November had 18. Of the 51 Canadians who made their NHL debut, 17 were born January to March and four October to December, none of them in December.
Every month from July on is short of Canadian NHLers
Share of players born in each month, against Canada’s births
Canadian NHLers born 1960-99 are 10-11% born in each month from January to May and 5.5-5.7% in November and December. For those born before 1950 every month was 7.5-9.2%, close to Canada’s birth calendar.
- Canadian NHLers born 1900-49
- Canadian NHLers born 1960-99
- All Canadian births 1991-2006
For players born before 1950 the bars run level, month after month. For players born since 1960 they tower from January to May and sag in the fall. Among Canadians born 1960-79, 32% were born January to March and 18% October to December, so a January-March birthday is about 1.8 times as common in the league. Canadian babies don’t follow that pattern. From 1991 to 2006, about 24% were born January to March and 24% October to December, and 50.3% in the first half of the year. That is a hair above an even spread. Measured against Canada’s real birth calendar, the NHL lean shrinks by less than a point.
Last season was the most January-heavy in almost a century
The lean hasn’t eased. In 2025-26, 64.2% of the 422 Canadians in the league were born January to June, the highest of any season since 1926-27; the previous high was 62.5%. Those players were mostly born from 1991 to 2006, when Canadian births were split about evenly.
Maybe the league just got younger. The youngest players lean hardest toward early birthdays, so a wave of rookies could push the count up on its own. The chart splits Canadians into two age groups to check.
Young Canadians are the most January-heavy, and the older ones have caught up a little
Share of Canadian NHLers born January to June, by age in that season
Show data
| Season | 23 or younger | 24 or older |
|---|---|---|
| 2005-06 | 59.0% | 58.7% |
| 2006-07 | 61.6% | 55.7% |
| 2007-08 | 63.6% | 52.9% |
| 2008-09 | 65.1% | 52.6% |
| 2009-10 | 59.7% | 53.7% |
| 2010-11 | 62.2% | 52.8% |
| 2011-12 | 64.4% | 53.1% |
| 2012-13 | 61.7% | 57.0% |
| 2013-14 | 71.0% | 56.3% |
| 2014-15 | 70.4% | 57.0% |
| 2015-16 | 68.0% | 55.3% |
| 2016-17 | 69.3% | 54.6% |
| 2017-18 | 65.2% | 58.6% |
| 2018-19 | 67.5% | 59.0% |
| 2019-20 | 68.5% | 56.7% |
| 2020-21 | 62.1% | 57.5% |
| 2021-22 | 60.0% | 59.5% |
| 2022-23 | 64.8% | 58.0% |
| 2023-24 | 69.5% | 59.2% |
| 2024-25 | 69.2% | 58.6% |
| 2025-26 | 69.7% | 62.3% |
- Reference: Even spread (49.6%)
The young players do lean harder: 70% of Canadians 23 or younger had January-June birthdays last season. But the older group moved too. Canadians 24 and up sat around 53% from 2007-08 to 2011-12 (53% in 2008-09) and reached 62% last season. Young players stayed roughly a quarter of the Canadians in the league the whole time. So last season’s high isn’t just a younger league.
It could still be a lucky year. With 422 Canadians in the league, luck alone can push a season a couple of points either way. A typical wobble is about 2.4 points. Last season sat about 2.0 wobbles above the 1980-2024 average of 59.3%. One season that far out turns up by luck now and then, so we’d want a second before calling it a trend.
Americans and Europeans have it too, a little less
If the lean were a quirk of Canadian minor hockey, players born elsewhere would be spread evenly. They aren’t. Gladwell told it as a Canadian story, and Canada does have the strongest lean. Americans and Europeans born from 1960 on sit only a few points behind, well above an even spread.
Canada leads, and every country sits well above an even spread
Share born January to June, by birth country and birth years (each player counted once)
Born 1960-79: Canada 61.5%, United States 56.8%, Europe 57.6%. Born 1980-99: Canada 61.2%, United States 58.0%, Europe 55.7%.
- Canada
- United States
- Europe
Every bar clears the even-spread line. Put everyone born 1960-99 together and Canada is at 61.4%, the United States 57.6% and Europe 56.5%. Canada leads the US by about 4 points. With groups this size, a typical wobble from luck alone is about 1.7 points, and Canada’s lead is about 2.2 of those wobbles. So it is probably real, but small.
Before 1950 there are too few to tell. Only 105 Americans and 68 Europeans born that early played in the NHL. The Americans lean late (38% January to June), most likely chance in a group that small.
The edge is biggest for players with short careers
So the January edge is real, and it isn’t only Canadian. It gets a lot of early-born kids to the NHL. It does less to keep them there. Players with short careers have the most early birthdays. Of Canadians born 1951-99 who played fewer than 100 NHL games, 61.5% were born January to June. Of those who lasted 800 games or more, 54.4%.
Up to now we have cut the year in half, so an even spread meant about 50%. The chart below cuts it into quarters, three months at a time, the way most birthday studies do. Now an even spread puts one player in four, 25%, in each quarter. Watch the gap between the two bars in each group.
The longer the career, the closer to one birthday in four per quarter
Canadian NHLers born 1951-99, by career regular-season games
January-March births fall from 31.7% of Canadians with under 100 games to 23.2% of those with 800+, and October-December births rise from 17.5% to 21.6%.
- Born January-March
- Born October-December
Among the short careers, January-March birthdays outnumber October-December ones almost two to one. Among the 800-game players the two bars nearly meet. One level down, in junior hockey, the gap is wider still. Barnsley’s count of 1983 rosters in the Western and Ontario junior leagues found 41.5% of players born January to March and 9.7% October to December. NHL rosters lean less. Frances Woolley of Carleton University summed up a Brigham Young University study of the 1,177 Canadians who played in the NHL between 2000 and 2010: “Twenty-nine per cent were born in the first quarter of the year.” The higher the level, the closer the count comes to one in four.
Among the players who last longest, the birthday edge fades
Go to the top of the ladder and the edge is gone. Of the 235 Canadians born since 1951 who played 1,000 games, 49.4% were born in the first half of the year, and more were born October to December (56) than January to March (45). Ray Bourque was born on Dec. 28, 1960, four days before New Year’s Day. He played 1,612 games, the most of any Canadian born late in the year since 1951. Of the 58 Canadian Hall of Famers born since 1951, exactly half were born January to June.
We picked those two groups after seeing the data. They make good stories, and they prove nothing on their own. The ladder is bumpy, too: players with 800 to 999 games are back at 60%. And 58 Hall of Famers is a small group. Luck alone could put the true figure for players like them anywhere from 38% to 63%.
The career chart is the part to trust. Its step-by-step slide fits what other research has found. A 2016 paper by Fumarco, Gibbs, Jarvis and Rossi, which studied NHL rosters from 2008 to 2015, found that later-born NHLers score more and earn more. Picture a boy born in November, in a league grouped by calendar year. Every minor-hockey season he plays against kids up to most of a year older, and he has to beat them anyway. The late-born players who reach the NHL have cleared a higher bar on the way in. Their birthday didn’t make them better players.
These are only the players who made it
Everything above comes from one place: the NHL’s own records, which list every player who played at least one game. They show how birth months shifted among the players who got in. They can’t show how many children played, how many quit, or why. A rising January share could mean more early-born boys reached the league, fewer late-born ones did, or both.
The closest thing to a real test came from Quebec. From 2002 to 2008 the province moved its minor-hockey cutoff to October 1, which should have helped boys born October to December. If the cutoff drives the lean, Quebec-born NHLers of the right age should show it. They didn’t, at least not clearly: 18% of Quebec-born NHLers born 1985-92 have October-December birthdays, against 17% for the rest of Canada. But only 67 Quebec-born NHLers were the right age, too few to show a shift either way.
Some late birthdays still get through
Matthew Schaefer was born in Hamilton on Sept. 5, 2007, a September birthday in the most January-heavy season in almost a century. Taken first overall in 2025, he played all 82 games for the Islanders last season at 18 and scored 23 goals, tying Brian Leetch’s NHL record for goals by a rookie defenceman. “It’s crazy. You don’t really think about that stuff,” he said. His coach, Peter DeBoer, put it more simply: “He’s a really, really special player.”
Lemieux signed with Pittsburgh 10 days after the draft. He and Roy went on to play 1,944 NHL games between them, and both are in the Hall of Fame. Two boys born in October, in the last three months of the year, the stretch that the 1984 Quebec study found filled fewer than one place in ten on the province’s top Pee Wee teams.
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Show the work
- Tests written down
- Not in advance (exploratory)
- Results computed
Birth date and birth country of all 8,776 players (skaters and goalies) in NHL bios for every regular season 1917-18 to 2025-26. Season charts count each player who played that season once; birth-group charts count each player once. Canadian shares are compared with Statistics Canada monthly births (1991-2025) and with an even spread by calendar days (49.6%); US and European shares only with the even spread. 95% ranges are Wilson intervals. Named players, the 1960-61 and 2025-26 month counts, the 1982-83 Oilers and the Hall of Fame flag (the bios’ isInHallOfFameYn field as of 2026-10-26) come from the same bios; the Oilers’ team comes from the season summaries. Counting seasons or games instead of players gives a January-June share 1 to 4 points lower after 1955, because later-born players last longer, and goalies (175 and 124 born 1960-79 and 1980-99) are within 4 points of skaters. The 1,000-game and Hall of Fame groups were chosen after seeing the data; we split them by odd and even birth years as a check.
| Test | Result | Verdict |
|---|---|---|
| Canadians born before 1950 show a January advantage | 49.9% January-June, n = 1,750 (95% 47.6-52.3%); odd/even birth years 50.5% / 49.4% | No |
More tests below
| Test | Result | Verdict |
|---|---|---|
| Canadians born since the mid-1950s are January-heavy | 61.5% (1960-79, n = 1,598); 61.2% (1980-99, n = 1,275); odd/even 1955-99 61.5% / 60.3% | Holds |
| Mostly Canadian | Born 1980-99: Canada 61.2%, US 58.0%, Europe 55.7%; pooled 1960-99 n = 2,873, 1,142, 1,339 | Strongest in Canada, present everywhere |
| Skew shrinks with career length (tiers set in advance) | Jan-Mar 31.7% (<100 GP, n = 1,607) vs 23.2% (800+ GP, n = 439); 600+ point skaters 55.1% Jan-Jun | Holds |
| The most durable and decorated Canadians (born 1951-99) are January-heavy | All players 60.2% (n = 3,551); 800-999 games 60.3% (n = 204); 1,000-1,199 games 46.8% (n = 158); 1,200+ games 54.5% (n = 77); 1,000+ games 49.4% (n = 235); Hall of Fame 50.0% (n = 58). 1,000+ games odd/even 47.3% / 51.9%; Hall of Fame 52.6% / 45.0%; 95% ranges 43.0-55.7% and 37.5-62.5% | No; post hoc, ladder uneven |
Continues below
| Test | Result | Verdict |
|---|---|---|
| 1960-61 was late-year-heavy among Canadians | December 23 of 151, the top month; Oct-Dec 49 vs Jan-Mar 40 | One season: a scene, not a test |
| The 2025-26 high (64.2%, the most since 1926-27) is just a younger league | 23 or younger 69.7%, 24+ 62.3% (2008-09: 65.1% / 52.6%); 2.0 SE above the 1980-2024 mean | No; one season, worth watching |
| Our bios match the published counts | 1982-83 all players 60.6% (n = 672) vs Barnsley 61.8% (715); Canadians 2000-01 to 2009-10 Jan-Mar 28.9% (n = 1,200) vs BYU 29% (1,177) | Holds, within about a point |
| Quebec’s October 1 cutoff (2002-08) shifted birth months | Oct-Dec 17.9% vs 17.3% for the rest of Canada (n = 67) | Too small to tell |
| Players born 2000-07 are even more January-heavy | 69.2% (n = 195) | Early arrivals only; careers still starting |
Frequently asked questions
Are most NHL players born in January?
More are born January to March than in any other quarter. About 32% of Canadian NHLers born 1960-79 were born January-March and about 18% October-December. Canadian births overall are close to a quarter in each. In 2025-26, February (53) and January (51) were the most common birth months among Canadian NHLers.
When did the relative age effect start in hockey?
Among Canadian NHL players, with those born from about 1953 on. Canadians born before 1950 were spread evenly across the year; the January-June share rose to 58% for players born 1955-59 and about 61% since. Addona and Yates (2010) dated the start to players born since 1951. In 1960-61, December was the most common birth month among Canadian NHLers.
Is the birthday effect only in Canada?
No. American and European NHL players born 1960-99 are 56-58% January-June, against about 61% for Canadians. Canada has the strongest lean.
Do players born late in the year do better once they reach the NHL?
The longer the career, the higher the share born late in the year. Among Canadians born 1951-99, October-December births are 17.5% of players with under 100 games and 21.6% of those with 800 or more. Published research has found later-born NHLers score more and earn more, consistent with a harder filter on the way up.
Are Mario Lemieux and Patrick Roy born on the same day?
Yes. Both were born on Oct. 5, 1965, in Quebec (Lemieux in Montréal, Roy in Quebec City), and both were drafted on June 9, 1984: Lemieux first overall by Pittsburgh, Roy 51st by Montreal. Both are in the Hall of Fame.
Are junior hockey players more January-heavy than NHL players?
Yes. Roger Barnsley’s count of 1983 Western and Ontario junior rosters found 41.5% born January-March and 9.7% October-December. A Brigham Young University study of Canadians who played in the NHL between 2000 and 2010 found 29% born January-March; counting the 2000-01 to 2009-10 seasons, we get 28.9%.
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Sources and method
- NHL stats (NHL.com), every season since 1917-18
- NHL stats API: skater bios (birth date and country), every season since 1917-18
- NHL stats API: goalie bios (birth date and country), every season since 1917-18
- Statistics Canada, Table 13-10-0415-01: Live births, by month (1991 to 2025)
- Roger H. Barnsley (2025), 40-years of relative age effects: life is not fair!, Frontiers in Sports and Active Living 6
- Simon Grondin (2024), To be or not to be born at the right time: lessons from ice hockey, Frontiers in Sports and Active Living 6
- Hockey Draft Central: 1984 NHL Entry Draft facts
- Georgia Straight, Charlie Smith: Malcolm Gladwell’s Outliers opens with tale about Vancouver Giants (Dec. 5, 2008)
- Frances Woolley, Carleton University: Making the NHL, does your birthday matter? (Nov. 22, 2010)
- Associated Press via Fox Sports: Islanders’ Matthew Schaefer ties Brian Leetch’s NHL record for goals by a rookie defenseman (April 2026)
- Trovato and Odynak, “Seasonality of Births”, The Canadian Encyclopedia
- Addona and Yates (2010), A Closer Look at the Relative Age Effect in the National Hockey League, JQAS 6(4)
- Fumarco, Gibbs, Jarvis and Rossi (2016), The Relative Age Effect Reversal among NHL Elite (MPRA 75691; reviews Barnsley et al. 1985 and 1988)
- Lavoie, Laurencelle, Grondin and Trudeau (2015), Temporal plasticity of the relative age effect in ice hockey: elite minor players in Québec
- Wang, Csiernik, Johnston and Baker (2025), Age effects in NHL draftees (current calendar-year cutoff)
Research and analysis, not betting advice. Past results do not guarantee future returns; bet only what you can afford to lose.