First off, excellent work on the Trout/Jackson comparison. It's hard to eliminate all the external variables in a small sample comparison of two players, but it seems like you came as close as possible to that ideal. And a fun read to boot. Second, don't think it's been mentioned yet, but in addition to Willihammer's helpful mention of the BRef info, there's also the FanGraph Ultimate Baserunning stat. It's the mirror image of Zone Rating for fielders, taking into account where batted balls go and how well a given baserunner produces relative to the situations they create. It includes things like first to second vs. first to third, staying out of the DP and advancing on tags, and other important factors. It cares not one whit about stolen bases, triples, or other traditional counting stat measures of speed. As an aside, it's figured into Fangraph's WAR ratings, which I didn't realize until this thread. In the case of Trout vs. Jackson, Hammer's excellent analysis corroborates UBR, or the other way around. Jackson has a nice UBR of 1.2 in 2012, which is just a hair below what the definition page categorizes as "above average". Trout scores a 5.0, halfway between "great" and "excellent". Not citing UBR as comprehensive by any means, but it seems useful, including even its definition/mission statement. It doesn't seek to define speed, because speed is a tool, not a skill. A heady player with good situational awareness and average speed can equal or even outperform a SPEEDy one on the basepaths. They can tag or take the extra base more often, get the split-second jump that prevents the double play, and above all, not get thrown out on an unforced advance.