As for our current legislative drama, it starts with a fairness problem that doesn’t get enough attention: If you get health insurance from your employer, you’re not paying taxes on the value of the policy. Holman W. Jenkins Jr. of The Wall Street Journal’s editorial page memorably referred to this mammoth giveaway as something that “perversely treats the richest taxpayers as the neediest.” Hence the original desire to give tax credits to everyone shopping for insurance on their own.

Then, however, the congressional maneuvering takes an interesting twist. If the Obamacare replacement bill had come forward (and become law) without any income caps on the health insurance tax credits, there was a good chance that employers would have stopped offering insurance to millions of employees. Not a good look. (The reasons are a bit complicated, but Christopher Jacobs of Juniper Research Group wrote a helpful explainer on it in The Federalist.)

But why the $75,000 and $150,000 benchmarks? There are two possible explanations. The first is principles: Congressional staff might have made a concerted effort to figure out at what income people might be able to afford future premiums without any help, given their other budgetary needs.

The second is practical and mathematical: Giving away tax goodies to even more affluent people would have cost enough to throw the numbers off when the Congressional Budget Office analyzes the bill in the coming days. A spokeswoman for the Ways and Means Committee said that both, in fact, were in play.

So, about those $150,000 families: Is that “middle income” label that the Republicans used truly applicable? Some experts do use income to define the middle, with the Pew Research Center putting “middle” in a range from 67 percent to 200 percent of median household income. That works out to roughly $48,000 to $145,000 for a family of four, based on numbers that the federal government published in 2015. Edward Wolff, a New York University economics professor, prefers a net worth measurement and a “middle” range up to $400,000.

Curious about where you stand? There are online calculators that will put you in your percentile based on household income. And the Henry J. Kaiser Family Foundation whipped up a tool this week to help people visualize the impact of the proposed tax credits.

Still, demographics do not capture feelings. Plenty of people with incomes above $200,000 are one missed paycheck (or a four-figure health insurance premium spike) away from real financial trouble. Sometimes they are to blame for picking an expensive community or getting into too much debt. But often they or their family members have fallen gravely ill, or an unexpected, undeserved and extended job loss has left them vulnerable even after they return to six-figure status.