Across Major League Baseball thus far in the 2007 season (through September 11), 74.5% of all stolen base attempts have been successful. This success rate is significantly higher than it has ever been since outs caught stealing began to be regularly recorded as a category of event. The league-wide stolen base success rate has been inching up in recent years but this season that success rate has taken a significantly new additional leap forward.

Adding up all stolen bases and stolen base attempts from 1957 through 2006, one finds that over that fifty-year period 66.6% of all stolen base attempts were successful. Before 2004, only in 1987 (70.1%) and 1995-96 (70.0% and 70.7%) did the overall MLB rate poke up briefly and slightly over the 70% threshold and in each case settled right back down within a year or two to the range of about 68% or so.

Over the past few seasons, however, the SB success rate has been rising a little bit each year, from 68.2% in 2002 to 69.4% in 2003, 70.2% in 2004, 70.6% in 2005 and then last season, 2006, the rate inched up again to its highest level of the past 50 years, 71.4%. And now, in 2007, instead of seeing any regression to a mean or any continued small increments of increase, we seem to be seeing a major acceleration of the recent increase in the SB success rate, from 71.4% in 2006 to 74.5% to date in 2007.

It is possible, perhaps, that in the last few weeks of the 2007 season a huge drop in SB success rates across MLB will bring the complete full-season number back within the expected historical range. But I can't think of a reason why stolen base success rates should drop significantly in late season games. Most likely the final 2007 numbers will look pretty much like the current rate between 74% and 75%, a result like nothing seen in the last 50 years.

What's happening here? I was curious to see whether the number of stolen bases has remained the same and just outs caught stealing have declined, suggesting players are getting faster or catchers slower, or alternatively whether stolen base attempts overall have declined, suggesting that teams are becoming more selective in their attempts and declining to run at all in lower percentage circumstances where they might have tried to steal previously. In general, the trend appears to be the latter – more selectivity.

Over the 1960s, teams averaged about .67 stolen base attempts (SBAs) by each team per game. In the 1970s that went up dramatically to about .96 SBAs per game. In the 1980s, attempts went up even a bit more, to about 1.1 SBAs a game. In the 1990s, attempts remained about 1.1 SBAs a game. But in the current decade of the 2000s, attempts have dropped dramatically to about .81 per game, and dropped to as low as .75 a game in 2005.

This drop in stolen base attempts presumably reflects a strategic reaction to the explosion of home runs in the late 1990s, which reduced the reward vs. risk ratio of stolen base attempts: the more likely it is that batter at the plate will hit a home run, the less rational it is for the runner on base to take the risk of trying to steal. But in the last couple of years, and especially in 2007, teams have seemed to learn that they had maybe grown a little too cautious, that if they exercise due care they can still take some extra steals without getting caught much more. Stolen base attempts have gone from .75 per game in 2005 to .80 in both 2006 and again so far this season. What has differed this season from last year is that of those .80 attempts per game in 2006, .57 represented successful steals and the other .23 were outs caught stealing, while this year .60 have been successful and only .20 have been outs caught stealing. With the most dramatic of the home run onslaught years apparently now behind us, teams seem to be intelligently readjusting their strategies to maximize stolen base attempt value – avoiding overly aggressive and risky attempts but not leaving high quality base advancement opportunities unused. The result is a rate of success on stolen base attempts that is unprecedented in the recorded history of such rates.

Are there differences in the stolen base success tendencies between the NL and AL? Both leagues are experiencing historically high success rates this season, the NL a bit higher than the AL, 75.4% in the NL to 73.6% in the AL, but the trend applies to both. The small edge in success rate for the NL matches the average edge the NL has had over the AL in success rates over the preceding 50 years, which has been about 1.6%. From 1957 through 2006, NL teams were successful stealing bases 67.4% of the time, compared to 65.8% of the time for AL teams, so both leagues in 2007 are ahead of their 50-year average success rate to an almost identical, and in each case very substantial, degree.

One other question that might be asked is whether the recent high level of stolen base success rates reflects a decision by teams to choose catchers more skilled on offense and less skilled at cutting down runners than in the past. Beginning in 1993 (coincidentally or not, the year of the most recent addition of major league expansion franchises), offensive performance by catchers, as well as by major league hitters generally, increased rather dramatically. Overall OPS in the majors in 1992 was .700, which had been about normal for many years – overall OPS had not been above .748 in any season since the 1930s. Then suddenly major league OPS jumped, first to .736 in 1993 and then to .763 in 1994, and has not been below .748 in any season since then. Catchers' hitting has followed along. After plodding along for years in the range of the .660s to the .680s, OPS by major league catchers jumped in 1993 to .714 and then to .727 in 1994, and has been below .700 only once (2002) since 1993.

Catchers as a group generally end up with an OPS in the range of 96% to 97% of overall league OPS, and that has been no different in the high offense, post-1993 years than it was before that. Over the full 50 years from 1957 to 2006, catcher OPS was 96.6% of major league OPS; from 1993 to 2006 that percentage was 96.5%. In 2007, catcher OPS is .712, actually a little bit lower than it has been on average since 1993 (.724). The increase in stolen base success percentage that is the topic of this article has occurred in just the last three or four years, and especially 2007. There is no indication that this increase is associated with any similarly recent jump in catcher offense, either an absolute jump or a jump relative to overall league offense.

For years prior to 2007, the underlying data on stolen bases, caught stealings, games played and league and catcher offense used in this article comes from Lee Sinins' marvelous Complete Baseball Encyclopedia database. I copied the relevant data into Excel and then added the appropriate formulas to get annual success rates and attempts per game rates. For 2007, I used the SB, CS and G data from the absolutely essential baseball-reference.com. For those interested, here's the stolen base success rate (SB/(SB+CS)) that I found for each year 1957-2007 and the stolen base attempts (SBA) per team per game ((SB+CS)/Games Started) for each year:

 	     SB 	        SBA Per Team 
Year      Success Rate      Per Game 
1957	    57.9%	            0.54
1958	    58.9%	            0.51
1959	    62.8%	            0.55
1960	    62.8%	            0.59
1961	    63.6%	            0.58
1962	    65.8%	            0.63
1963	    61.8%	            0.62
1964	    62.1%	            0.58
1965	    64.8%	            0.69
1966	    61.1%	            0.74
1967	    59.4%	            0.71
1968	    61.9%	            0.75
1969	    62.3%	            0.76
1970	    63.9%	            0.77
1971	    62.9%	            0.72
1972	    62.1%	            0.78
1973	    62.6%	            0.84
1974	    64.3%	            1.00
1975	    64.8%	            1.01
1976	    66.4%	            1.19
1977	    62.9%	            1.14
1978	    65.0%	            1.10
1979	    65.1%	            1.09
1980	    67.2%	            1.16
1981	    64.8%	            1.12
1982	    66.3%	            1.14
1983	    67.3%	            1.17
1984	    66.7%	            1.08
1985	    68.4%	            1.08
1986	    67.2%	            1.17
1987	    70.1%	            1.21
1988	    69.9%	            1.12
1989	    68.4%	            1.08
1990	    68.5%	            1.14
1991	    66.6%	            1.11
1992	    67.1%	            1.16
1993	    66.3%	            1.08
1994	    68.6%	            1.03
1995	    70.0%	            1.04
1996	    70.7%	            1.01
1997	    67.9%	            1.08
1998	    68.6%	            0.98
1999	    69.3%	            1.02
2000	    68.8%	            0.87
2001	    68.8%	            0.93
2002	    68.2%	            0.83
2003	    69.4%	            0.76
2004	    70.2%	            0.76
2005	    70.6%	            0.75
2006	    71.4%	            0.80
2007¹	    74.5%	            0.80

¹ through 9/11/07

Bruce Regal is a New York attorney, with an avocational interest in baseball. He maintains Metaforian, a blog devoted to the New York Mets and Baseball.