Are Elo ratings comparable across history?

Question

It is fun to speculate how the great players of today would fare against those of the past.

With the advance in knowledge of the openings, particularly aided by computers, a leading modern player would have a great advantage against one from history. Probably, Carlsen would have Morphy, Capablanca, or Fisher (playing at their respective peaks) trussed up like a roasting turkey by move 15 or 20, simply because of his opening expertise. For this reason, one would expect the Elo ratings of modern top players to exceed those of their historic peers.

In one way, the comparison seems unfair. If modern experts played those from history, starting from a dynamic post-opening position with approximately equal fighting chances for both sides (as judged by a computer), who would win then? Would this be accurately reflected in the comparative Elo ratings? If so, this would go with top Elo ratings being restrained from a general upward drift.

Answer 1

Statistician and ratings expert Jeff Sonas writes

"[A] rating always indicates the level of dominance of a particular player against contemporary peers; it says nothing about whether the player is stronger/weaker in their actual technical chess skill than a player far removed from them in time. So while we cannot say that Bobby Fischer in the early 1970's or Jose Capablanca in the early 1920's were the "strongest" players of all time, we can say with a certain amount of confidence that they were the two most dominant players of all time. That is the extent of what these ratings can tell us." (source)

His own project Chessmetrics attempted to estimate playing strength across history for various players (see site overview).

Sonas uses a "a weighted and padded simultaneous performance rating" to enable comparisons across eras.

There are challenges but Sonas discusses this in some detail during his 15 Aug 2023 interview on the Perpetual Chess Podcast (ep. 343).

_{Related: The Historical Comparison of Players}

Answer 2

I am not a statistician, so I can't speak to the accuracy of ELO ratings across time, but as a historian, I would say that comparing players from different eras is ultimately a flawed (if fun) project because they are acting with the specific knowledge of their time period and playing with the goals of people of their time.

Given a dynamic, post-opening position, contemporary elite players would almost always beat past elite players. This is because they would know more endings, have a larger knowledge base of known positions and how to play them, and understand how middlegame positions work better (i.e. the benefits of advancing of a and h pawns are only recently really understood).

For example, Morphy would be brilliant, but he would be looking for Morphy-like combinations while Capablanca or Karpov would be looking to restrict those possibilities with solid positional play. Morphy would probably react poorly because the elements of positional play (as we understand it) had not even been articulated yet.

Different elite GMs and champions have different goals. Anderssen to create works of beauty, Tarrasch to articulate sound principles of play, Fischer to crush his opponents, etc. It's hard to measure this if the players' goals and motivations are totally different.

This doesn't even bring up the question of time control, which has not been standard throughout history. Like, how would Botvinnik do without having recourse to adjournments?

The idea of chessmetrics to try to determine a player's relative strength to his contemporaries is a good method to understand some aspects of player strength, but it is not as solid when comparing people across time, as Morphy and Philidor, for example, did not have access to really strong competition.

One would really wonder what would happen if Morphy or Lasker or Keres had access to chess theory today, but that is another question...