Body: <p>I've downloaded and parsed the <a href="http://www.kingbase-chess.net/" rel="noreferrer">king-base chess database</a> (about 1.5 million games) and am looking at distribution of moves for games. When plotting the distribution for different outcomes, I see spikes at 80, 100 and 120 moves (and smaller spikes for draws at 20, 40 and 60 moves).</p>
  
  <p><a href="https://i.sstatic.net/fOYk3.png" rel="noreferrer"><img src="https://i.sstatic.net/fOYk3.png" alt="enter image description here"></a></p>
  
  <p>Why are these spikes occurring? Are people more likely to resign at these round numbers? Or are there rules in professional games that mean games are more likely to end after multiples of 20 moves?</p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-04-07T11:45:45.263Z
Comments.Text: Are these half-moves or moves (a move by both sides)? I'd expect a spike at 40 full moves.
Comments.UserDisplayName: RemcoGerlich
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-04-07T12:45:54.980Z
Comments.Text: @RemcoGerlich I grouped white and black moves into "move-pairs" to smooth the data. Otherwise the data is very spiky. For example White is much more likely to win on an even move (white gives checkmate) rather than an odd move (black resigns).
Comments.UserDisplayName: Peter Jones
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2017-04-07T13:15:37.097Z
Comments.Text: @RemcoGerlich - ah sorry, these are half-moves
Comments.UserDisplayName: Peter Jones
Tags: <statistics>
Title: Why are games more likely to last 60, 80 and 120 moves?
ThreadText: # Why are games more likely to last 60, 80 and 120 moves?
  
  (Asked by: username_0 on 2017-04-07)
  
  I've downloaded and parsed the [king-base chess database](http://www.kingbase-chess.net/) (about 1.5 million games) and am looking at distribution of moves for games. When plotting the distribution for different outcomes, I see spikes at 80, 100 and 120 moves (and smaller spikes for draws at 20, 40 and 60 moves).
  
  [![enter image description here](https://i.sstatic.net/fOYk3.png)](https://i.sstatic.net/fOYk3.png)
  
  Why are these spikes occurring? Are people more likely to resign at these round numbers? Or are there rules in professional games that mean games are more likely to end after multiples of 20 moves?
  
  **Tags:** statistics
  
  > **Comments:**
  > **username_1**: Are these half-moves or moves (a move by both sides)? I'd expect a spike at 40 full moves.  
  > **username_0**: @username_1 I grouped white and black moves into "move-pairs" to smooth the data. Otherwise the data is very spiky. For example White is much more likely to win on an even move (white gives checkmate) rather than an odd move (black resigns).  
  > **username_0**: @username_1 - ah sorry, these are half-moves  
  
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  ## 0 answers
  
  