Because then I'd wonder, if you had two franchises at 7 WAR per year, bottom half of roster ... how many players did each team churn through? A team that churned 25 scrubs a year might be more "futile" in their pyramid; one that churned only 15 might have gotten the support it wanted for the better top of roster, or something. But yeah, absolutely.
You'd have the question of how many of the 0.3 WAR player seasons were by talented rookies who went on to play well a season or two later, a Justin Smoak type, versus another 0.3 WAR player who was a terrible middle infielder lucky to get what he did.
Injury luck could vary. The proportion of minor league value could be different even for the same Scrub return between teams; a team with a tall, skinny pyramid might have "shimmed" its pyramid by playing one Willie Bloomquist for lots of years. So you'd look at years-per-Scrub. Stuff like that.
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But that's over-thinking it and just my way of chasing my tail - your measurement would give 85, 90, 95% of what we wanted to know, I think. If you feel like drawing up any data on that I'd be grateful.
Personally would like to know what it looked like with Gillick excluded, and would take Scrubs as everybody after the top 8-10 ML players. From 1990 (when Griffey 'arrived') to today, I've got a hunch the Mariners' talent pyramid has been much, much worse after its top 10 ML players than ANY other team in baseball.
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Great stuff Matt. You don't chime in enough on the study-design end as well as on other things :- )