A rather more gentle treatment of Mark Bittman’s misunderstandings:
Bittman’s observation is correct, and first principles are an excellent start to the process of logical deduction. But it is also an appalling place to end the process of thinking. True, we don’t all have to stand on the shoulders of giants and reach further and higher than the pebbled seashore, but those previous generations of billions did contain some bright people who did think about the problems of the human condition. Some of them even came up with interesting answers.
The economist looks at Bittman’s statement and notes that healthcare is a luxury good – as our real incomes rise we spend more of our incomes upon it. Food is an inferior good – as incomes rise a smaller portion of total income is spent upon it. As our incomes rise, the portions that we spend on different things change. This is the same insight as Maslow’s Pyramid that denotes the hierarchy of human desires. As we satisfy our desires on the lower level of the pyramid, we allocate more of our rising income to the upper levels of the pyramid. This is what those definitions of luxury goods and inferior goods mean.