how do you figure that 1/5 of working americans have negative discretionary income?
By looking at the chart that you yourself posted?
Did you read your own links? look at discretionary income by decile at the bottom of the second
the bottom decile means that the bottom 10 percent of americans have a discretionary income between $0 and $11,000
so 1/10, not 1/5. and of that 1/10, most of them are probably not left with $0 discretionary income, let alone negative discretionary income
note that discretionary income means after paying your taxes and your necessities like rent, so 10% of $11,000 could fund someone's comfortable retirement if they're able-bodied and under 30
and this is especially achievable once we realize that people don't remain in the bottom decile. they get raises, they get employer matches, they move in with room mates or with significant others, they get married, etc.
They also start getting sickness, diseases, disabilities once they start aging past mid 40s as most people do start to develop problems as that's part of aging. Medical issues that cost money, and in a capitalistic environment those medical issues can suck away a persons entire life savings.
this is why we have health insurance, and it's also why we should combat obesity and smoking as just those two avoidable things represent 30% of our yearly healthcare expenditures, and that's just in known costs.
we're a fat and unhealthy population, but that's especially exacerbated by our sedentary lifestyle and poor diets ---