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A Comparison of Two Seasons: 1968 and 2018

Introduction

As we all know, there are particular trends in MLB baseball that may be problematic, at least from the fans perspective. In the 2018 season, the proportion of balls in play is at its lowest value in baseball history. Strikeouts are up — actually it seems that baseball currently is dominated by pitching. That makes one think of the 1968 season (50 years ago) when MLB thought the game was unbalanced in favor of pitchers. In that case, rules were changed — the pitcher’s mound was lowered by five inches starting in the 1969 season — and this rule changed had a significant impact on the game.

Anyway, these thoughts motivated a quick exploration to compare baseball in these two pitching-dominated seasons. All of these graphs were prepared using Retrosheet play-by-play and game logs for the two seasons.

Length of the Game

One obvious difference between 1968 and 2018 baseball was the length of the game. Below I construct parallel boxplots of the lengths (in minutes) of all games in the two seasons. Quite a large difference — the median length of a game in 1968 was 150 minutes (2 1/2 hours) and it is currently 180 minutes (3 hours). Games tend to be a half-hour longer in 2018.

Runs Scored

Using the Retrosheet game logs, I next looked at the total runs scored in a game. Below I display side-by-side barplots of the percentages of runs scored for the two seasons. For example, we see that 5 percent of games had only one run in 1968 — the corresponding percentage was 2 percent in 2018. The most common total runs scored was 5 in 1968 compared to 9 in 2018. It was much more likely in 2018 to have more than 10 runs scored in a game. I’m not sure we want to return to the low-scoring affairs in 1968.

Margin of Victory

How close were the games in the two seasons? Below I show side-by-side barplots of the percentages of the margin of victory in 1968 and 2018. For example, note that 35% of the games in 1968 were decided by a single run, compared with 27% of the games in 2018. Over half of the 1968 games had a margin of victory of 1 or 2 runs. It was much more likely to have a blowout in the 2018 season. If you like close games, then a 1968 game would be more desirable to watch than a 2018 game.

Outcomes of a Plate Appearance

One big difference between the two seasons is the distribution of the different outcomes of the plate appearance. Using the EVENT_CD variable in the Retrosheet play-by-play files, I collected the proportion of plate appearances in each season that were HR, HBP, SO, Double, BB, Single, Triple, IP_out (an out that is not a strikeout), Fielder’s Choice, Error, or an Intentional BB.

It is tricky to compare these different proportions for two seasons because the variation in the proportions depends on the size. For example, variation in a proportion of a rare event like a HBP will be small, but variation in the proportion of a common event like an in-play out will be large. To fix this variation issue, I convert all proportions to logits, where a logit of a proportion p is equal to log(p) – log(1-p). Below I look at the difference in logits: logit(2018) – logit(1968) for each of these PA outcomes. I color the point by being in-play or not in-play. The black vertical line shows no change between the two seasons.

The basic message from the graph is that the in-play events like singles, triples, ip_out, fielder’s choice, errors are all down in 2018. In contrast, many of the “not in-play” events (HR, HBP, SO, BB) are up in 2018.

This show how baseball has changed compared to 1968. Much of the activity is happening just at home plate or outside of the park (a home run) and there is much less activity in the rest of the field. I think fans are missing much of the in-play activity like good running around the basepaths and good defensive plays, and these activities are not that common in the current season.

Number of Pitchers Used

Another dramatic difference in baseball in the two seasons is the number of pitchers used in a game. Below I show parallel barplots of the number of pitchers used in a game in 1968 and 2018. In the 1968 season, the most common number of pitchers used (by both teams) were 3 and 4. In 2018, the most common number of pitchers rose to 8, and it was relatively common to use 10 or more pitchers.

Takeaways

I don’t think we want to return to 1968-style baseball. But there several attractive features of 1968 games compared to 2018 games:

  • 1968 games tended to be a half-hour shorter than 2018 games
  • games were closer in 1968 — more games were decided by 1 or 2 runs
  • more in-play events –small-ball was more popular in the 1968 season
  • there were fewer pitchers used in 1968 which resulted in more complete games and less time delays in replacing pitchers

It may be desirable for MLB to add some new rules to shorten games and create more in-play activity. Some of the rule changes (actual and proposed) appear to have little impact on the game, such as the elimination of the four-ball intentional walk or restricting the defensive shifting of infielders. But any proposed change has to carefully studied to see if it will have the intended impact on the game.

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