Answers.Body: <p>There is a tradeoff between making the pairings that "should" be made according to the strict pairing rules, and attempting to prevent collusion.  Imagine this scenario:</p>
  
  <pre><code>Russia 1: 8.5
  Russia 2: 8
  India:    8
  Peru:     7.5
  </code></pre>
  
  <p>Which is more unfair: to have Russia 1 play Russia 2 and have a possible prearranged result, or to <em>prevent</em> Russia 1 and Russia 2 from competing, causing Russia 2 to play a team with a lower score instead of the strong Russia 1 team?</p>
  
  <p>There are several ways to handle this.  You could switch the pairings only when it does not cause a team to be moved up or down a pairing group. You could switch the pairings in any round except the last two. Or you could not switch them, and watch closely for signs that the players aren't playing seriously.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-09-30T15:18:53.587Z
Answers.LastActivityDate: 2018-09-30T15:18:53.587Z
Answers.UserDisplayName: D M
Body: <p>Doesn't it create bias for the country?</p>
  
  <p><strong>Disclaimer</strong>: I realize that benefits of having more teams from the same country far outweigh possible drawbacks, just trying to reason how possibly "unfair" can this be for the other teams, and / if this can be improved.</p>
  
  <p>Imagine last decisive round where two teams from the same country are paired between each other. Will it be a fair match? Does it make sense to avoid such pairings?</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-09-30T11:29:28.163Z
Comments.Text: Are you talking about the chess olympiad 2018? It's common that the host team sends out multiple teams.
Comments.UserDisplayName: SmallChess
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2018-09-30T11:33:50.457Z
Comments.Text: Yes, but nevertheless.
Comments.UserDisplayName: Ivan Balashov
Tags: <swiss-pairing>
Title: Multiple teams from the same country in Swiss system
ThreadText: # Multiple teams from the same country in Swiss system
  
  (Asked by: username_0 on 2018-09-30)
  
  Doesn't it create bias for the country?
  
  **Disclaimer**: I realize that benefits of having more teams from the same country far outweigh possible drawbacks, just trying to reason how possibly "unfair" can this be for the other teams, and / if this can be improved.
  
  Imagine last decisive round where two teams from the same country are paired between each other. Will it be a fair match? Does it make sense to avoid such pairings?
  
  **Tags:** swiss-pairing
  
  > **Comments:**
  > **username_1**: Are you talking about the chess olympiad 2018? It's common that the host team sends out multiple teams.  
  > **username_0**: Yes, but nevertheless.  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_2 on 2018-09-30. Score: 4 | Accepted answer
  
  There is a tradeoff between making the pairings that "should" be made according to the strict pairing rules, and attempting to prevent collusion. Imagine this scenario:
  
  ```
  Russia 1: 8.5
  Russia 2: 8
  India:    8
  Peru:     7.5
  
  ```
  
  Which is more unfair: to have Russia 1 play Russia 2 and have a possible prearranged result, or to *prevent* Russia 1 and Russia 2 from competing, causing Russia 2 to play a team with a lower score instead of the strong Russia 1 team?
  
  There are several ways to handle this. You could switch the pairings only when it does not cause a team to be moved up or down a pairing group. You could switch the pairings in any round except the last two. Or you could not switch them, and watch closely for signs that the players aren't playing seriously.
  
  
  ---
  
  