Medicaid, meanwhile, is sliced up into different programs depending on whether you're an adult, a child, and so on. The Individual Market has the Obamacare exchange crowd (who mostly receive financial assistance) and "off-exchange" enrollees (who have to pay full price).
But Wait There's More
OK, so there's 18 different categories, plus a bunch of people who are still uninsured for one reason or another? Confusing, but not "thousands of categories" confusing, right? Well, here's the thing:
Each state has its own Medicaid program. Each state has its own rules and market for Large Group, Small Group, and Individual Market insurance. Medicare may be a single, federally run program ... but a whole lot of people in it are actually managed by Private insurance companies through "Medicare Advantage" instead of the government.
So you're really talking about several hundred programs or markets. Even in Public insurance programs like Medicaid, each state can have up to eight different eligibility categories depending on whether you're, say, a pregnant woman, a newborn baby, a toddler, a teenager, an adult, or a ghostly apparition whose only desire is to rob people of their sacred tax dollars.
Like Vizzini from The Princess Bride, wait 'til I get going! Because even within each state, there are "Rating Areas" for insurance companies to price health insurance premiums, which can be as small as a few zip codes or as large as the entire state, though most cover a few counties. There are over 3,100 counties in the United States. And there may be as few as one or as many as 20 different companies offering insurance policies in each one, so you do the math. No, seriously, stop and do the math right now.
It'll be on the final.