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Did you know that some umpires are more steal-friendly than others?

I have to admit, that possibility had never crossed my mind until a
recent discussion on Usenet’s rec.sport.baseball
mentioned a couple of articles in
previous years’ STATS, Inc. books that addressed the relationship between
umpires and stolen-base percentage. The earlier of those two articles
showed a seemingly wide disparity between umpires on steals: some called
out over 40% of would-be basestealers, while others called out fewer than 20%.

That got me wondering who the toughest and easiest umps to steal on are
today. I looked at the combined numbers from 1999 and 2000 (through last
Sunday’s games) and considered only steal attempts of second base. Among
umpires who worked more than 750 innings at second base, here are the five
with the highest percentage of would-be basestealers called out:

Umpire            SB  CS    CS%
-------------------------------
Chuck Meriwether  55  41  42.7%
Paul Schrieber    47  35  42.7%
Mark Carlson      38  28  42.4%
Tim Welke         45  32  41.6%
Rick Reed         62  44  41.5%

And here are the ones with the highest percentage of safe calls:

Umpire            SB  CS    CS%
-------------------------------
Mike Everitt      59  11  15.7%
Ed Montague       72  18  20.0%
Jerry Crawford    55  14  20.3%
Angel Hernandez   87  25  22.3%
Wally Bell        59  17  22.4%

At first glance, it certainly appears that some umps are more prone to
call a runner out on a steal attempt than others. Over a two-year period,
Chuck Meriwether was about two-and-a-half times more likely than Mike
Everitt to send a would-be basestealer back to the dugout. That CS% split
is not all that different from the split between the most and least
successful catchers over that same period–Ivan Rodriguez at 47.4% and
Dave Nilsson at 14.0%, respectively (again, considering only steal attempts
at second).

Is it possible that the differences are just due to chance, that there
really is no "basestealing bias" among umpires? After all, both
STATS, Inc. and I ran statistical significance tests on the data we used,
and neither of those tests found a significant relationship between umpires
and steal percentage. In this case, though, I think the significance tests
got the results they did because the sample sizes weren’t large enough, and
other evidence points pretty strongly to the existence of the basestealing
bias.

The first, and most compelling, piece of evidence: Doug Drinen, in the
aforementioned newsgroup discussion,
looked at a much larger collection of games in the 1980s, with the data courtesy of the
wonderful folks at Retrosheet. He
found that Terry Cooney called out 46% of basestealers, while Larry Goetz
called out only 23%, each in over 550 steal attempts. That kind of
disparity in that large a sample would be pretty much impossible if there
were no relationship between umpires and steals.

Another piece of evidence pointing to a basestealing bias is that there is
a positive correlation between the umpires’ caught-stealing percentage
between 1999 and 2000. The correlation is fairly weak (a coefficient of
0.26–not too surprising since we’re talking about only around 50 attempts
per umpire per year), but it’s still strong enough to indicate there is a
signal coming through the noise.

So, while there’s plenty of work left to do to determine exactly how large
and how prevalent the effect is, I feel safe stating that there is an
umpire effect on CS%. And I feel safe concluding that the umpires in the
first table above are, as a group, less friendly to stolen bases than the
umps in the second table.

That brings me to the really interesting question: do major-league
baserunners and managers do anything about it? Do they track the
umpires’ caught-stealing numbers, and then run sparingly on the tough
umps and freely on the easy ones? Let’s take a look at our two extreme
groups again, measuring the frequency of steal attempts against them
(expressed here as steal attempts per 18 half-innings worked at second
base). First, the "Don’t tread on me" crowd:

                     SB Attempts
2B umpire              per Game
----------------------------------
Chuck Meriwether         1.54
Paul Schrieber           1.35
Mark Carlson             1.58
Tim Welke                1.64
Rick Reed                1.78
----------------------------------
AVERAGE                  1.57

And now the "Buy first base, take second free" crowd:

                     SB Attempts
2B umpire              per Game
----------------------------------
Mike Everitt             1.56
Ed Montague              1.59
Jerry Crawford           1.41
Angel Hernandez          2.01
Wally Bell               1.37
----------------------------------
AVERAGE                  1.59

And there you have it: there’s virtually no difference in the rate of
steal attempts between the most steal-friendly and the most steal-hostile
umps. Even though teams do pay close attention to catchers in their steal
decisions (teams run against weak-armed Mike Piazza more than twice
as frequently as they run against strong-armed Ivan Rodriguez), and
even though umpires could have the same sort of effect on CS% as catchers,
runners attempt steals against the toughest umps in the league just as
often as they do against the easiest.

I don’t want to make too big a deal of this. Even if runners and managers
were to take umpires into account in their basestealing decisions, the
benefit to most teams would be small, maybe a handful of extra runs per
season. Still, given that teams have always tried to squeeze out every
extra run they can through bookkeeping and strategy, it’s a little
surprising that this strategic opportunity has apparently escaped them.

Michael Wolverton can be reached at mjw@baseballprospectus.com.

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