On the 22nd of November, the Twitter user @AlberGN2 published a statistic that collected the average duration of each of the 32 pieces that participate in a chess game. Obviously, the pieces that last the longest are the kings of both colors, since they cannot be captured and therefore eliminated. But, beyond the kings, it is surprising to note that the piece that, on average, lasts the longest in a game, is the "h" black pawn which, according to statistics, holds about 37 moves.
The study was released on the website of Chessvision. Its author, who wanted to go deeper into the asymmetries of chess, used the database Lichess Elite, created by Nikonoel. This repository includes 403.000 games between players of more than 2400 ELO and players of more than 2200 on the platform. Once obtained the games, the creator developed a code that allowed to identify to each piece by its square of beginning and to value its evolution within the games.
The most general conclusion that can be obtained when viewing the material is that the analyzed games have an average duration of 42 moves. It is surprising to note that both kings have the same estimated life span, which denotes a balance in the results of the chess games. On the other hand, the piece that has less useful life is the white pawn of "d", which tends to disappear after 21 moves.
But before entering into more precise conclusions, let's look for patterns common to several sets of parts:
- Kingside pawns last longer than queenside pawns. When the last queen-side pawns (the "a" pawns on each side) disappear, there are still four king-side pawns left. In addition, of the 7 pawns with the shortest life span, 5 belong to the queen's side and 2 (those of "e") to the king's side.
- Bishops, without being one of the pieces that last the longest, endure more than knights. Knights are the pieces - excluding pawns - that take the least time to play a game of chess, according to statistics. Without counting the "d" pawns, the four knights would be the pieces with the shortest life span on the board. However, bishops do not last much longer either, since they occupy the positions from the ninth to the twelfth. In addition, the knights of "b" last longer than those of "g" on both sides. It is the same with the bishops of "f". All this compilation regarding the minor pieces makes us think that the main material asymmetries produced during a chess game are determined by exchanges between knights and bishops.
- The rooks have a longer life span than the queens. Both queens on average have the same durations in chess games, about 29 moves. It is not a coincidence that they have a similar average life span, since it is normal that they are exchanged or that both end the game. But, it is curious to observe that rooks have an average life span of 34 moves. This statistic clearly reflects that the most common endings are those of rooks. On the other hand, it is important to note that black rooks last slightly longer than white rooks, which would show that, in the case of material asymmetries, white rooks have a greater tendency to form part of them than black rooks, although the differences are minimal.
- The pawns of "d" have the shortest life span. The explanation is simple. One of the first objectives during the opening is the occupation of the center of the board and, therefore, both sides will try to fight their central squares (e4, e5, d4, d5). There it is common for pawn exchanges to take place. One could give a thousand examples of openings that end with captures of "d" pawns. Without going any further, the main line of the most played opening, the Sicilian, presents the following moves: 1. e4, c5. 2. Nf3, d6 (2...e6, 2...Nc6, 2...g6, etc.) 3. d4, cxd4. This central change of pawns occurs in more than one million of the games collected by Yottabase. Therefore, it justifies the statistics obtained.
- The pawns that last the longest are, in order, "f", "a", "g" and "h". The pawns of "f", "g" and "h" are those that cover the short castling. When castling we try to weaken as little as possible the pawn structure that protects our king. Although, as always, there are exceptions, it is logical to think that these are the pieces with the longest useful life of the 32. The pawn "a", on the other hand, has a tendency to remain isolated on the queen's side or, on the other hand, its duration could be explained by the possible defense by the rook of "a" or the pawn of "b" which, although they have less useful life, it does not go much beyond 2 or 3 moves.
The statistics published by Chessvision give cause to find multiple parallels in the chess positions and in the lifetime of the 32 pieces. The conclusions we have drawn here are the product of observation. If you notice other similarities you can comment on our social networks.
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