Player absence and betting lines in the NBA

•We examine the efficiency of betting lines in the NBA when players are absent.•Opening lines have substantial biases when a (high-quality) player is absent.•All biases are removed by game time (the closing line is a 50-50 bet).•NBA betting market participants accurately price the absence of players.

We examine the efficiency of betting lines in the NBA when players are absent. We show that the betting line tends to move away from the team with absences, particularly when a meaningful player is absent. We show that opening lines set by bookmakers have significant errors in games when a player is absent. No profitable betting strategy exists in wagering at the closing line, however, as biases are removed by either the sportsbook responding to new information or the sportsbook responding to the actions of bettors.