After creating the catalog of FIDE Knockout Events, with links to the pages for specific events, I gathered the games for the ten events that had played a role in the last ten World Championship cycles. Then I loaded the PGN header data for those games into a database.
The ten events include 3968 games, more or less. I haven't been consistent in how I treat first round forfeits -- sometimes there's a record of the forfeit in the event's PGN games (e.g. 1999); sometimes there isn't (e.g. 2004). After creating the database I started looking at different aspects of the data.
The following chart shows a count of the number of games played at each stage of the first round of each event. The first column is the round number (I have similar charts for the other rounds) and the second column is the game number within that round. As you would expect, the counts are identical for games 1 and 2, because each mini-match in a round consists of at least two games, with the players switching colors for the second game. The chart gives a bird's-eye view of the evolution of FIDE's regulations for the knockout tournaments.
For example, the first three events -- 1997, 1999, & 2000 -- show that slightly more than half of the 128 players had a game in the first round. This is because the top players were seeded directly into the second round, where we find 32 mini-matches for the 64 players remaining. FIDE abandoned this strategy for the 2001 knockout and afterwards.
The counts for games 3 and 4 show the number of first round matches that went into tiebreak. The counts for game 5 and afterwards show the number of matches that required further tiebreak. In 1997, a 'sudden death' portion of the match started in game 5; in 1999, it started in game 7 (after a second two-game tiebreak, as it did starting round two in 1997).
In 2001, sudden death was replaced by a single Armageddon game in game 7. This appears to have been the case through 2007. (I say 'appears', because I haven't been consistent about recording then-current regulations on the pages for the ten tournaments. This would make a useful follow-up project.)
In 2009, the format changed dramatically. The first tiebreak was a four-game match (games 3 through 6) followed by a series of two-game blitz matches. One first round match, Akobian - Tregubov, was only decided after five blitz matches, Akobian winning both games of the last match.
In 2011, the format reverted to two-game tiebreaks, with one additional tiebreak match before the Armageddon game in game 9. According to the Regulations for the World Chess Cup 2015, the same format will be used for the knockout event later this year.
There is plenty of over-the-board drama hidden behind these dry statistics, and the counts show only the first of the seven rounds in each of the ten events. I'll try to unearth some of that drama in a future post.