A Steady Slog Toward Three Outcomes Baseball

During this quiet winter of baseball, I’ve entertained myself with a mild obsession with the three true outcomes (not outfits).  Dave Cameron took note of the three outcomes trend in early April 2017, only one week into the new season.

 “…while samples are still tiny for players and teams, things tend to stabilize pretty quickly at the league level. And, not surprisingly, the first week of the season was filled with the two things MLB games are becoming known for; strikeouts and home runs.”

Cameron goes on to predict a record year for the three true outcomes in 2017.  He was right.

A steady slog towards three outcomes baseball

Figure 1 is an update of Bill Petti’s analysis back in 2012.  It looks at the average rate of the three outcomes by player for each season since 1913.  The top blue line shows the proportion of plate appearances that have resulted in either a home run, strikeout or walk across seasons.  I got here pretty easily: Like Bill, for each player, I added their home runs, strikeouts and walks in a season and divided that by the number of plate appearances.  That provides the proportion of three outcomes plate appearances for each player.  Unlike Bill, I used at least 170 plate appearances in a season as my cut off (rather than 500).  Then, for each season, I found the average proportion of three outcomes plate appearances for eligible players.  I followed this procedure for home runs, strikeouts and walks separately.

The trend of the blue line is clear: players’ average rates of three outcomes have increased starting around 1920, dropping off a bit in the 70s, and continuing on through 2017.  There has been a spike in recent years, and the 2017 average rate of 33% three outcomes is clearly the highest since 1913.

It is interesting to look at each outcome separately as well.  The tremendous growth in strikeout rates is clearly a big part of this story.  Average walk rates have consistently hovered around 8 or 9 % of plate appearances after peaking just over 10% in 1948.  Home run rates are increasing, but home runs are still rare compared to the other outcomes.  Through the 1940s average home run rates per player averaged around 1% of plate appearances.  They jumped to around 2% in the 1950s, and stayed pretty consistent until the mid-1990s.  Since then they have been increasing and peaked in 2017 with an average of 3% of plate appearances.

What does this trend towards three outcomes mean for the game?  Perhaps Cameron subtly showed his feelings about it when he titled his essay, “The League’s Continuing March Towards Three Outcomes Baseball.”  A march; a steady march.  Figure 1 suggests an uphill march.  Cameron could have called it the race towards three outcomes.  Or the growing excitement of three outcomes baseball.  Even the uphill battle of three outcomes baseball sounds more engaging than a march.  Is three outcomes baseball more of a slog than it is an exciting new dynamic in the game?