As a result, the differences in what poor and middle-class families consume on a day-to-day basis are much smaller than the differences in what they earn.

“There’s just a whole lot more assistance per low-income person than there ever has been,” said Robert Rector, a senior research fellow at the conservative Heritage Foundation. “That is propping up the living standards to a considerable degree,” he said, citing a number of statistics on housing, nutrition and other categories.

Decades of economic growth, however, have been less successful in raising the incomes from work of many poor families, prompting a strong conservative critique this year that hundreds of billions of dollars in antipoverty programs have failed to make the poor less dependent on government.

“That’s the crux of the problem,” Mr. Rector added. “What sort of progress is that?”

But another form of progress has led to what some economists call the “Walmart effect”: falling prices for a huge array of manufactured goods.

Since the 1980s, for instance, the real price of a midrange color television has plummeted about tenfold, and televisions today are crisper, bigger, lighter and often Internet-connected. Similarly, the effective price of clothing, bicycles, small appliances, processed foods — virtually anything produced in a factory — has followed a downward trajectory. The result is that Americans can buy much more stuff at bargain prices.

Many crucial services, though, remain out of reach for poor families. The costs of a college education and health care have soared. Ms. Hagen-Noey, for instance, does not treat her hepatitis and other medical problems, as she does not qualify for Medicaid and cannot pay for her own insurance or care.