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Born at the Wrong Time: Selection Bias in the NHL Draft


  • Robert O Deaner
  • Aaron Lowen
  • Stephen Cobley


Relative age effects (RAEs) occur when those who are relatively older for their age group are more likely to succeed. RAEs occur reliably in some educational and athletic contexts, yet the causal mechanisms remain unclear. Here we provide the first direct test of one mechanism, selection bias, which can be defined as evaluators granting fewer opportunities to relatively younger individuals than is warranted by their latent ability. Because RAEs are well-established in hockey, we analyzed National Hockey League (NHL) drafts from 1980 to 2006. Compared to those born in the first quarter (i.e., January–March), those born in the third and fourth quarters were drafted more than 40 slots later than their productivity warranted, and they were roughly twice as likely to reach career benchmarks, such as 400 games played or 200 points scored. This selection bias in drafting did not decrease over time, apparently continues to occur, and reduces the playing opportunities of relatively younger players. This bias is remarkable because it is exhibited by professional decision makers evaluating adults in a context where RAEs have been widely publicized. Thus, selection bias based on relative age may be pervasive.

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  • Robert O Deaner & Aaron Lowen & Stephen Cobley, 2013. "Born at the Wrong Time: Selection Bias in the NHL Draft," PLOS ONE, Public Library of Science, vol. 8(2), pages 1-7, February.
  • Handle: RePEc:plo:pone00:0057753
    DOI: 10.1371/journal.pone.0057753

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    1. Fumarco, Luca & Gibbs, Benjamin & Jarvis, Jonathan & Rossi, Giambattista, 2016. "The Relative Age Effect Reversal among NHL Elite," MPRA Paper 75691, University Library of Munich, Germany.
    2. Bryson, Alex & Gomez, Rafael & Zhang, Tingting, 2014. "All-Star or Benchwarmer? Relative Age, Cohort Size and Career Success in the NHL," IZA Discussion Papers 8645, Institute of Labor Economics (IZA).
    3. Alessandro Pluchino & Alessio Emanuele Biondo & Andrea Rapisarda, 2018. "Talent Versus Luck: The Role Of Randomness In Success And Failure," Advances in Complex Systems (ACS), World Scientific Publishing Co. Pte. Ltd., vol. 21(03n04), pages 1-31, May.
    4. Luca Fumarco & Benjamin G Gibbs & Jonathan A Jarvis & Giambattista Rossi, 2017. "The relative age effect reversal among the National Hockey League elite," PLOS ONE, Public Library of Science, vol. 12(8), pages 1-16, August.
    5. Christian Thue Bjørndal & Live S Luteberget & Kevin Till & Simen Holm, 2018. "The relative age effect in selection to international team matches in Norwegian handball," PLOS ONE, Public Library of Science, vol. 13(12), pages 1-12, December.
    6. Sergio J Ibáñez & Aitor Mazo & Juarez Nascimento & Javier García-Rubio, 2018. "The Relative Age Effect in under-18 basketball: Effects on performance according to playing position," PLOS ONE, Public Library of Science, vol. 13(7), pages 1-11, July.
    7. Javier Brazo-Sayavera & María Asunción Martínez-Valencia & Lisa Müller & Georgios Andronikos & Russell J J Martindale, 2018. "Relative age effects in international age group championships: A study of Spanish track and field athletes," PLOS ONE, Public Library of Science, vol. 13(4), pages 1-11, April.
    8. Michael Romann & Stephen Cobley, 2015. "Relative Age Effects in Athletic Sprinting and Corrective Adjustments as a Solution for Their Removal," PLOS ONE, Public Library of Science, vol. 10(4), pages 1-12, April.
    9. Alfonso de la Rubia & Christian Thue Bjørndal & Joaquín Sánchez-Molina & José María Yagüe & Jorge Lorenzo Calvo & Sergio Maroto-Izquierdo, 2020. "The relationship between the relative age effect and performance among athletes in World Handball Championships," PLOS ONE, Public Library of Science, vol. 15(3), pages 1-21, March.
    10. Youwei Wang & Yuxin Chen & Yi Qian, 2018. "The Causal Link between Relative Age Effect and Entrepreneurship: Evidence from 17 Million Users across 49 Years on Taobao," NBER Working Papers 25318, National Bureau of Economic Research, Inc.

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