I don't know why or how things have changed from the beginning of the 2008 season until the end of the 2014 season in MLB. Analytics, defensive shifts, different approaches to pitching and hitting, changes to park configurations, recruitment of elite athletes into player roles, the decline (we think) of performance enhancing drugs -- there are lots of things that could cause some or all of this.
I am not qualified to untangle the Gordian Knot of "How" or "Why". I'm just putting out a reference tool for all of you to see how baseball has changed. I picked 2008 arbitrarily because it interests me as a Phillies fan. I know my rooting interest has declined relative to the league, but today I am more interested in how the league has changed.
"There's less offense!" Yes, but how much less? That I can show through data from fangraphs. The "How?" and "Why?" are really interesting questions to discuss.
PART 1: Hittin' Season, or Where Have All the Dingers Gone?
Thanks, Fangraphs for this data.
It's not just home runs. Look at extra base hits. Triples seem to fluctuate pretty wildly, but doubles and home runs are down considerably.
The reduction in doubles is an unwavering, perfect downward trend with no deviations for all 8 years - it goes down somewhat every single year. That is remarkable, and it has caused the disappearance of about 900 doubles per year, or 30 per team (and 60 total bases). That's a Jimmy Rollins or Chase Utley, just immediately Revere'd. I could see a defense-related argument for this, but that's a scientific wild ass guess (SWAG, in the scientific parlance).
The home run trend is far less clear, but it has been a pronounced decline from 2008 through 2014. The difference between 2013 and 2014 is especially striking, though no defensive changes can account for balls hit over the fence, and inside-the-park homers are so rare that they don't affect the data meaningfully. I'll get to fly ball percentages and HR/FB ratio later, don't worry. Smushing a straight line on the HR number from 2008 through 2014 gives us a reduction of 692 dingers a year, or 23 per team (and 92 total bases). A whole 2008 Jayson Werth has been killed off on every single team in MLB.
Singles are down, too. Defense? The data are less clean than with the doubles, but it's not a bad bet. There were 771 fewer in 2014 than in 2008. That is 25 per team, or about 1/6th of a hit per game. Total hits are down by 2,377, or 79.23 per team, which is about 0.5 hits per game (and more total bases).
Walks are waaaaay down, both the unintentional and intentional variety. This is no doubt in recognition of the value of the Oh Bee Pee. The dropoff is about 2,300 and 300, or 2,600 fewer baserunners (and batters faced and pitches thrown...) or about 87 runners per year (close to one half per game).
Hit by pitch, stolen base (and caught stealing) are all pretty much unchanged. There are fewer sacrifice flies (fewer runners, probably) and fewer sac bunts (the realized cost of the out and fewer chances, maybe?). RBI and runs scored are down. Grounded into Double Play (GDP) numbers are down as well, though fewer baserunners seems plausible as an excuse for part of that. Also our next major issue...
Strikeouts are waaaay up.
There were 4,557 more whiffs in 2014 than 2008, and all of them were not from Ryan Howard. That's an extra 152 per team per year. That's a lotta sombreros.
Fangraphs tells us more.
On Base Percentage used to be about .333 in 2008. The MLB average was .314 in 2014. Slugging is down: .416 to .386. Isolated power is down: .152 to .135. OBP + Slugging (the vaunted "OPS") has declined from .749 to .700. That decline is less than the difference between 2008 Pedro Feliz and 2008 Jimmy Rollins, but it isn't far off. An average MLB player today OPS-es close to how Geoff Jenkins did in 2008. Oof.
The batted ball data from Fangraphs produced the chart above. Fly balls (producing home runs and some doubles) are down. Line drives are flat. Ground balls are up. Infield hits are up. Bunt hits are up dramatically, but the overall numbers are small. The HR/FB rate bounces, but looks pretty much trendless. This, read together with the hitting data above on strikeouts and walks, looks like a FIP/SIERA/xFIP approach to pitching -- try to induce ground balls, do not be a fly ball pitcher, don't walk dudes, and strike people out.
Pitchers may not be better, but the are pitching smarter. Except they may also be better. Look at the pitch data:
The obvious starting point is fastball velocity, which has increased in every single year, rising from 90.7 to 91.8. Sliders are faster - 82.7 to 83.7. Cutter velocity is up; curveball velocity is up, etc. Every kind of pitch is being thrown faster. Pitchers are throwing harder. They may be better athletes, mechanics may be better, surgery might be better, who knows? They are just throwing harder.
The pitch mixes have changed, too. Straight fastball use has declined from 60.70% to 57.70%, which is about a 5% drop. Sliders have become less used as well, dropping from 15.6% to 13.70%. Cutters and curves appear to have picked up the slack as secondary pitches. Changeups, splitters, and knuckleballs are all pretty much unchanged.
This approach to pitching (not just the velocity) may account for some of what we see in terms of more strikeouts and reduced offensive output.
I put this together not because I am looking for some unified field theory of baseball, but because a recent commenter was discussing what a league average IFFB% was, and I did not have a handy reference. Now I do, and I will bookmark this, since it gives me a handy reference for K%, BB%, line drive%, HR/FB%, etc. We now can see easily and quickly what is "league average" for hitters in all kinds of cool categories.
Why has league average changed? That's for you folks to figure out.