June 21, 2009
Prospectus Idol Entry
Are Offensive Shortstops Becoming Toxic Sub-Prime Mortgages and Other Evolutionary Trends in Baseball Positions
In March 2002, Baseball Digest said we were living in "the era of the shortstop." After all, the late 1990s ushered in a crop of offensive-minded shortstops like Alex Rodriguez, Miguel Tejada, Derek Jeter, and Nomar Garciaparra. The article included the Royals' Neifi Perez, but given the benefit of hindsight, I'll leave him out of the discussion. A popular conception was that this represented a new era where the once defense-dominated position was no longer going to be a wasted spot in the batting order. As the other teams scrambled to keep up with the Joneses, was something lost in the process? Is the quest for the next batch of power-hitting shortstops leaving defense in its wake? To answer this question and others, we will use the Win Shares system to help us.
Our Data Workbench: The Win Shares System
In 2002, Bill James published his book on Win Shares, which the dust jacket claimed was "a revolutionary system ... for player evaluation." For those readers who are not familiar with it, the Win Shares system allocates a portion of each team's wins for the season to each player based on his statistical performance. These Win Shares are categorized into three groups: batting/base-running, fielding, and pitching. For a more detailed description (and believe me, it is detailed as James needs about 100 pages to describe all the mechanics) the reader can either buy the book or use one of the following on-line articles as a jumping-off point: Tom Tango's website, Wikipedia, or BaseballGraphs.com.
While the objective of this article is not to debate the efficacy and accuracy of this metric, the reader should be aware that there were some initial criticisms. With that said, the folks at BaseballGraphs and The Hardball Times have made refinements to the calculations to resolve many of these issues. The data that I used in this article was downloaded from the BaseballGraphs website and gives the Win Shares for each player-team-year combination from 1900 to 2008.
Since fielding Win Shares are key to this article's analysis, it should be noted that one of the main criticisms is how the Win Shares methodology addresses fielding. Much of the criticism is that it doesn't use the more advanced defensive metrics that have been developed in the last few years. Some of its fielding calculation simplicity is because games from the early twentieth century lack the play-by-play data of the Retrosheet era (1954 - present) and the consistent batted ball information (1989 - present) from recent games. James wanted to have a system that could use readily available statistics and go as far back into history as possible. Current independent research by Colin Wyers uses some probabilistic modeling to allocate the uncharted hits to improve the approximation of the average number of hits in aggregate that should be assigned to a given fielder, and will still allow fielding statistic calculations as far back as 1871. As this methodology gets refined and potentially incorporated into the Win Shares calculations, it will be interesting to see if the allocated fielding shares change significantly.
Typically the focus of Win Shares has been on the value of a given player relative to others. As I started looking at the data, I became more interested in looking at Win Shares in aggregate to see how the game (and more specifically, each individual position) has evolved.
The (De-)Evolution of the Middle Infielder
What have baseball teams expected from each position in terms of the trade-off between offense and fielding and has this changed through the years? To address this question, I plotted the percentage of that position's Win Shares that come from fielding versus its total Win Shares over the last 11 decades.
To no one's surprise the positions up the middle (C, 2B, SS, CF) have a higher percentage of their value in fielding as compared to the corner positions (1B, LF, RF). One does see the transformation of third base from a significantly defensive position to the more offensive position it is today. It seems that this switch started in the 1930s and was completed by the 1950s.
By standard variability metrics (standard deviation, range of high to low), the middle infielder, especially the shortstop, has seen the greatest fluctuation (mathematically) in how they contribute to a team's winning. One sees a potential golden age of shortstop defense in the 1970s. For the first time since catchers at the turn of a century, over half the value of a position came from the glove instead of the bat. Wyers' data suggest that the under-appreciated Mark Belanger, the prototypical 1970s' shortstop, was the fielding equal of the consensus defensive wizard, Ozzie Smith. The current Win Shares methodology though has him the fifth best defensive shortstop since 1960 behind Smith, Dave Concepcion, Cal Ripken, and Omar Vizquel.
The new era of the offensive shortstop began in the early eighties with Robin Yount, Ripken and Alan Trammell (all solid defenders), with the first two winning back-to-back AL MVP awards and leading their team to the World Series in 1982 and 1983, respectively. Despite the steady increase in the shortstop's value from his bat in the 1980s and 1990s, it was still primarily a defensive position (45% average value from fielding) as compared to the expectations in the 1930s to 1960s (42% average value from fielding). It's in the 2000s that teams truly pushed the envelope on a shortstop's offensive production to a level of importance that hadn't been witnessed since the turn of the century.
On the other side of the bag, we see a similar but much more gradual trend with second basemen. Their defensive peak came in the 1960s and 1970s, only to see the emphasis shift back to offense again in the 1980s with the emergence of players like Ryne Sandberg, Lou Whitaker, and Willie Randolph and continue through the 1990s and 2000s with Roberto Alomar, Craig Biggio, and Jeff Kent. At this time, one has to consider the question of causation. Are these curves of the middle infielder shaped because that was the type of talent that was available at the time, or was it a change in how the position was valued? To help us address this question, let's consider the value of a given position relative to the rest of the team.
A Position's Value to the Team
The graph below is a plot of the percentage of each position's Win Shares as compared to the total Win Shares of the team (for legibility I have limited it to just 1B, SS, CF, and the maximum of the corner OF spots).
Our Golden Age of Shortstop Defense seems like a misinterpretation of the initial data. Given that there are eight positions, our expectation is that, on average if we assume equal importance, each position should garner roughly 12.5% of a team's Win Shares (the thick black "Equal Value" line). It's a little less starting in 1973 to reflect the inclusion of the designated hitter as a position player. Except for the 1900s, the shortstop has always been less than this "equal-value" point, and hit its ultimate low in the 1970s, as shortstops accounted for only 9.1% of the team's position player value, the lowest point of any position by a long shot. The return of the offensive shortstop was the correct move as an overemphasis on defense was causing the shortstop position to become irrelevant.
There are two other interesting trends that emerge, both related to power. As the game historically switched from triples to home runs, we see the decline of the center fielder and the emergence of the first baseman. The first baseman peak of the 1930s is essentially caused by just two exceptional players in that decade (Lou Gehrig and Jimmie Foxx). From the 1900s to the 1920s, the average team got most of its value from its centerfielder. From the 1930s to 1960s, the centerfielder was still second in value as the corner outfielder reigned as the preeminent value position. Only in the last twenty years has the first baseman dominated all other positions. In general, the catcher (11.3%), second baseman (11.5%) and third baseman (11.8%) have all held pretty steady as to the percentage of team value from these positions, only varying by a few tenths of a percentage from this average in any decade.
Has the Pendulum Swung Too Far?
The return of the offensive shortstop was a solid evolutionary move as the pendulum had placed significant emphasis on defense in the 1970s, but is it in danger of going too far the other way? Let's plot the percentage of a team's batting Win Shares and fielding Win Shares that are claimed by the shortstop.
It is now clear that the 1970s weren't such the defensive golden age as we initially thought. If they were, we would expect to see an increase in the fielding Win Shares claimed by shortstops in the 1970s. In fact, we actually see a decrease from the previous four decades. The spike of the 1970s that we saw in the first chart was caused by the offensive futility of the shortstops of the decade. Why this dearth of shortstops who could hit? Was it just luck, or something programmatic? Beyond the luck explanation, I offer two possible theories:
From the 1900s to the 1990s, the shortstop had usually garnered 18.2% of a team's fielding Win Shares. This was always the case within a few tenths of a percent. As teams began to realize the offensive black-hole of shortstops that occurred in the 1970s, a break from the past occurred and more emphasis began to be placed on the need for production out of the position. If one looks at the great batch of offensive shortstops of the 1980s and 1990s, their fielding win-shares were just as solid as their counterparts.
Since the batch of offensive shortstops from the 1990s provided such a competitive advantage to their clubs, other teams followed suit. Unfortunately, there just aren't enough offensive shortstops that are also good defenders out there to meet the demand, so teams began lowering the defensive requirements. For the first time in the history of the game, we have begun to see a significant decline in shortstop fielding, as they only captured 16.2% of their team's fielding Win Shares, a 10% decrease from the previous decade's 17.9%. Keep in mind that this decline in defense is partially due to shortstops that fit the new offensive-first mold (Jimmy Rollins and Jose Reyes), but also results from the initial 1990s crew that saw their defensive abilities decline but weren't moved because of their perceived offensive value at a premium defensive position (Derek Jeter and Nomar Garciaparra).
So how does this relate to sub-prime mortgages? I'll use a gross over-simplification of the global credit crunch to illustrate. Having a few sub-prime mortgages, which have both higher reward and higher risk, can be a good thing, as the basics of portfolio optimization will tell you. However, as banks needed higher levels of return to compete for the consumer's assets dollars, they moved more assets into the higher return sub-prime vehicles, and therefore needed more sub-prime loans. To increase the supply pool of candidate sub-prime loans, they needed to lower the requirements bar (thus increasing the level of risk) for future loans. In much the same way, baseball teams in the 2000s lowered the defensive ability bar in order to increase the supply of offensive shortstops. If teams want (or feel a need) to further increase the supply pool of offensive shortstops, we should expect to see further degradation in the fielding Win Shares that shortstops claim in the coming decade.
Given that the shortstop in the 2000s is still below his "equal-value" point as compared to the other positions and the percentage of total Win Shares captured by shortstops increased in the 2000s, this has been a favorable move. Up to this point, the overall benefit (improved offense) has outweighed the loss (decreased defense). Some in the industry sense getting close to the tipping point. One can look at two of many examples:
However, if the trend continues, you'll want to prepare your kids for the following analogy question on the SAT in 2022:
The correct answer may be (b).