Castling short looks like the most dangerous move in chess, and the truth is stranger: it is a trick of how we write moves down. O-O is the one move with a symbol of its own, while every knight move is split across a dozen spellings, so castling wins a count it was never really in. Group blunders by the PIECE that moved instead and castling is the smallest category there is.

Castling short looks like the most dangerous move in chess, and the truth is stranger: it is a trick of how we write moves down.

O-O is the one move with a symbol of its own, while every knight move is split across a dozen spellings, so castling wins a count it was never really in. Group blunders by the PIECE that moved instead and castling is the smallest category there is.

O-O tops the list for 59 of 239 players and is about 1.1% of any one player's blunders, measured across 299,635 games containing a move that cost at least 300 centipawns. Read it as a fact about counting, not as advice: newsroom_corpus_worst_piece() puts castling at 1.4% of blunders against the queen's 19.8%.

Across 299,635 analysed games from 239 players.

The Position

White to move and win.

White to move · rated 1899.

The answer runs in tomorrow's issue.

Eloist puzzle deck

The Opening Files · No. 5

A game without a blunder is the exception.

For the typical player in the corpus, 20.4% of their games contain no blunder at all, about one in five, with the middle half of players between 16.2% and 24.9%. Measured across 458,186 analysed games from 246 players.

The figure is the median PLAYER's rate, not the corpus average: one prolific account holding a sixth of the games would otherwise be reported as though it were everybody. Playing a clean game is not the standard an amateur is failing to meet; it happens about one game in five.

Across 458,186 analysed games from 246 players.

The Opening Files runs again tomorrow.