What percentage of the population is truly incapacitated in such a way as to preclude productivity?

One question I have long had is what the base line population might be in terms of true non-productivity.

What I mean is that everyone (or most people) can support some concept of transactional insurance. You are a hard worker with a track record of sustained employment. Suddenly your industry declines or you are injured and out of work for a year or so. In those type of cases, often characterized as deserving cases, I believe most people would be inclined towards significant generosity. And I suspect, with a lot of red-tape and missteps, we do in fact take somewhat reasonable care of the deserving cases.

But everything exists on a continuum of some sort. Where does deserving separate from undeserving?

This goes to the larger issue of definitions of poverty. For example, in the US the base poverty rate has hovered around 15% for decades. Partly this is because poverty, for federal purposes, is defined not in absolute terms but in relative terms. Our poorest quintile of citizens have household incomes equal to those of middle quintile Europeans.

What I have long wondered is about that ever changing population of 15%. Who is deserving (deserving of temporary of temporary assistance to get back on their feet) and who is long term destitute? This is in turn partly an issue of productivity. Who has the Knowledge, Experience, Skills, Values, Emotions, and Behaviors (KESVEB) to recover from some external disruption and continue a productive life versus who is long term unproductive and can we distinguish in this latter group between those who unproductive because of genuine disability versus unproductive because of bad decision-making versus unproductive as a life choice?

I would have gueesed that the 15% was divided along these lines:

Deserving, 1%
Disabled, 2%
Decision-making, 7%
Life choice, 5%

This book is long dated but at least a partial answer: Families, Poverty, and Welfare Reform: Confronting a New Policy Era edited by Lawrence B. Joseph. ON page 153 he indicates that 50% are on welfare for more than ten years and 75% are on welfare for at least five years. That doesn't answer the question but does indicate that the number who are "deserving" is in fact a relatively low percentage.