The first few moves of a chess game, known as the chess opening, are one of the most-studied aspects of the game, largely because of how important they can be. If you don’t start off with a good opening, you could doom yourself to defeat before the game really even begins. It’s therefore no surprise that one of the key steps to becoming a skilled chess player is studying and memorizing the many varieties of openings.

If you’re familiar with chess, you know how quickly the set of possible moves grows with each move a player makes. After White and Black’s first turn, the board will be in one of 400 unique positions. After their second turn, there are 197,742 possible positions. And after only 3 turns, 121 million possible positions. This means that if you play enough chess, it’s highly likely that you will play a game that no one has ever played in the history of our universe.

Despite the infinite possibility in chess, there appears to be a strong bias toward a small subset of openings. In this data set, there were roughly 4,000 unique openings, and the 30 most popular ones comprise 70% of all chess games.

Whereas there were less than 100 unique openings by the end of both player’s second turn in 1850, there were over 1,000 unique openings by 2014. This may be an artifact of the data set, however, because there are far more games recorded in the 21st century in this data set.

Via Randal Olson for the full article, more stat porn charts, more historical context.