The question is purposefully ambiguous: I'm interested in various operationalization of "slack" as a fraction of one's resources. I'm interested in knowing the distribution across the present human population.
It could also be that the concept is fundamentally confusing in some ways, like we all have 0 slack because any action could make the difference between reaching longevity escape velocity and not. I'm also interested in comments along those lines.
WOW, I didn't expect to see this post here, as a new member of EA and longstanding but frequently-infrequently-frequent member of the church of the subgenius looking to move things forwards in my life I had quietly begun to refer to EA as church of the genii.
The question is definitely an interesting one that much of my own thinking touches towards from reading Enneagram, Briggs Meyers, assorted philosophy and being a mostly silent member in many forums for these. I'm assuming with both EA and Subgenius there is a large number of INTJs or other NT types,
My internal answer to the problem largely lies with the idea of levels of consciousness from enneagram mapped with identifying as an INTJ myself such for that INTJs (I haven't put much thought into generalising this otherwise) the amount of slack would be proportional to the levels in that at each stage the amount of consciously directable slack would be greater but so would the need to 'do something with it' in part to maintain it.
Of course is fiendishly difficult to define in any objective assessment so maybe Robert Anton Wilsons "Reality is what you can get away with" provides a more objective stance in that the amount you can afford to get away with is the gross amount of slack.
Sorry this is a bit waffly.
For a post like this, I think you'll get much better answers if you offer a definition of what you mean by "slack", perhaps with some links to posts that originally coined the definition you are using (I assume you're referring in part to this post).