*is amused at the idea that you can measure poverty in that sort of way*
Well, something is being measured. Call it what you will.
We like statistics, and HHS has come up with the definition of poverty as a "family of four living at or below an income of $22314 per year." Other incomes for other family sizes, of course. And, technically, the income thresholds do vary with age of family members in their full algorithm. The US Department of agriculture provides food costs data. There are something like 48 different thresholds in use. But obviously it's a statistical yardstick, and not a complete description of poverty in the abstract sense.
Whatever you make of it, it's an objective, time-varying parameter, and it's now at 46.2 million people. That's huge. Highest level in the 52 years that the statistics have been collected.
The aggregate GDP may be increasing, and that may have economists saying that the recession was brief, and finished about 2 years ago, but maybe other indicators besides GDP growth should be given more weight in the minds of policy makers. This poverty index is just one of those indicators.
It's the highest raw number of people in 52. It's nowhere near the pre-Great Society percent. It is the highest precent since the early 90s recession. And the GOP is 100% convinced that cutting capital gains taxes or the large inheritance tax and all other taxes that primarly hit richers is the solution for people in poverty