Probability and Kings' Birthdays, seriously...

In Sunday's fit of boredom, I added a column for birthdays to the Kings reserve list (the master list that contains all the players under contract plus unsigned draft picks and players playing in Europe whose rights are controlled by the team). I decided it would be useful to have that information next to the waiver and draft data. In Monday's fit of boredom, I made a list of birthdays by month and day only (you know, for all of those birthday parties we like to throw here at SBN).

There are 68 players on the list (actually now there are only 65, but I put this together pre-Ersberg and a couple other deletions). How many do you suppose share a birthday with another player on the list? Not talking about years here, just month and day.

(Yes, this is a math problem. No, it has nothing to do with hockey. This is what happens when you have four days off.)

Sixty-eight players with sixty-eight birthdays. How many have a birthday on the same day as another player in the Kings organization?

Would you believe 18? Slightly better than 1/4. Here's the list, chronologically by birthday:

Trevor Lewis 1/8
Martin Jones 1/10
Jack Johnson 1/13
Kyle Clifford
Viatcheslav Voynov 1/15
Jonathan Quick 1/21
Oscar Moller 1/22
Jarret Stoll 1/24
Robert Czarnik 1/25
Brad Richardson 2/4
Andrew Campbell
Kevin Westgarth 2/7
Ray Kaunisto
Thomas Hickey 2/8
Johan Fransson 2/18
Ryan Smyth 2/21
Jake Muzzin
Juraj Mikus 2/22
Garrett Roe
Nicolas Deslauriers
Corey Elkins 2/23
David Kolomatis 2/25
Bud Holloway 3/1
Derek Forbort 3/4
Kevin Gravel 3/6
Erik Ersberg 3/8
Brandon Kozun
Colten Teubert
Michal Handzus 3/11
Constantin Braun
Marc-Andre Cliche 3/23
Justin Azevedo 4/1
Alexei Ponikarovsky 4/9
Jordan Weal 4/15
Willie Mitchell 4/23
Tyler Toffoli 4/24
Rich Clune 4/25
Patrick Mullen 5/6
Matt Greene 5/13
Nic Dowd 5/27
Andrei Loktionov 5/30
Peter Harrold 6/8
Jeff Zatkoff 6/9
Jordan Nolan 6/23
Dwight King 7/5
David Meckler 7/9
Podge Turnbull 7/12
Jean-Francois Berube 7/13
Linden Vey 7/17
Mikhail Lyubushin 7/24
Andrei Shefer 7/26
Alec Martinez
Jonathan Bernier 8/7
Brady Murray 8/17
Brayden Schenn 8/22
Anze Kopitar 8/24
Wayne Simmonds 8/26
Scott Parse 9/5
Justin Williams 10/4
Michael Pelech 10/6
Dustin Brown 11/4
John Zeiler 11/21
Davis Drewiske 11/22
Drew Doughty 12/8
Igor Melyakov 12/23
Maxim Kitsyn 12/24
Rob Scuderi 12/30
Jan Marek 12/31

The most common illustration of this effect: take any group of 23 people (e.g. the active roster of one NHL team, or a classroom of kids). The odds of any two people in a group of 23 sharing the same birthday is just better than 50%. That is, half the time, if you check the birthdays on the roster of a sports team (if they have 23 players or more), you will find at least one pair of players who share a birthday. Try it next time you're looking at your $10 program between periods.

With 57 people, the odds are higher than 99% that there will be at least one match. So it's not probably/possibly not so surprising that the Kings reserve list of 68 has 18 different matched pairs. I say it's not surprising, but I am still surprised by it every time.

If you're interested in getting into the numbers, the gist is described by Wikipedia as The Birthday Problem.