THE MEN WITH THE GOLDEN ARMS: Great piece by Michael Wolverton at Baseball Prospectus regarding the correlation of runners cought stealing by catchers from year to year. This earlier piece demonstrated just how much a catcher's throwing arm can make up for a relative offensive deficiency. For another example, see this ESPN.com piece comparing Ivan Rodriguez and Mike Piazza. In sabermetrics, much of the action over the last few years has been in measuring aspects of defensive performance. The best part of Bill James' New Historica Baseball Abstract was the defensive component of James' Win shares method, which extends his offensive formulas to measuring defensive performance.
In the current Wolverton piece, he notes that a further column will examine the deterrent effects of a catcher's arm (i.e., how runners may stop trying to steal on a catcher) and how to measure such effects. In the New Historical Baseball Abstract, Bill James states that teams steal more often when they are ahead than when behind, meaning that bad teams face more stolen base attempts than good teams. It thus appears that a true measurement of a catcher's arm would have to take into account not only the deterrrent effects of a catcher's arm, but also the team's won-lost record. Perhaps James has a formula for adjusting expected stolen-base attempts based on a team's won-lost record. We await publication of his Win Shares book for the answer.