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Medicare is government-regulated health coverage that most of us will receive at some point, with many millions benefiting from it right now. There's a lot that you probably don't know about the critical program, though. Here are nine stats about it that will likely surprise you.

57 million

There are more than 57 million enrollees in Medicare, as of August 2016. Considering that there are roughly 325 million people in America, that's a hefty 18% of the population -- nearly 1 in 5.

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17.3 million

Among the 57 million above, more than 17 million enrollees are estimated to have signed up for Medicare Advantage plans in 2016. You may have heard about these plans, which are alternatives to the Part-A-plus-Part-B original Medicare package, but you probably weren't aware just how popular they've become. (They are required to offer at least as much coverage as original Medicare, and most offer more, with out-of-pocket expenses capped.)

$1,288

The sum above is the deductible (for 2016) tied to Part A coverage of original Medicare (which covers hospital inpatient care, skilled nursing facility care, and some home healthcare and hospice care). You might think that it's not a particularly shocking stat, but get this: It's not a simple annual deductible. Instead, it applies per "benefit period," with a benefit period beginning when you are admitted to a qualifying facility and ending once you've not received inpatient care for 60 consecutive days. Thus, if you are in and out of hospitals frequently, you may have to pay that deductible several times in a single year.

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7 months

Enrolling in Medicare late can be very costly, upping your Part B premiums (which cover medical services, but not hospital services) by 10% for each year that you were eligible for Medicare but didn't enroll. So know when your "Initial Enrollment Period" is. It's the three months leading up to your 65th birthday, the month of your 65th birthday, and the three months that follow. You may avoid the penalty, though, if you're already receiving Social Security benefits by the time they reach age 65, as such folks are typically enrolled in Medicare automatically. You might also avoid it if you're still working (with employer-provided healthcare coverage) at age 65, or if you're serving as a volunteer abroad.

2%

Relatively few people realize that the Medicare system has a five-star rating system for services and facilities such as hospitals, dialysis centers, Medicare Advantage plans, nursing homes, and more. A five-star rating is the best you can get, but among hospitals, only about 2% (102 out of close to 4,600 in the U.S.) earned it. About 20% were awarded four stars -- which should make it clear that a lot of healthcare facilities are not top-notch and have significant room for improvement. The rating system for hospitals takes into account measures such as the rate of post-surgical infections and emergency room wait times. Medicare Advantage plans are evaluated  on measures such as how well they're keeping their members healthy (via screenings, checkups, and more), how well they're managing members' chronic conditions, and how good their customer service is. Drug plans are rated on measures such as how well member appeals are handled, customer satisfaction, and how well the plan does on safety and accuracy in managing prescriptions.

$0

That's how much you'll have to pay for an annual wellness visit with your doctor, per Medicare. It's also how much you'll pay when you get certain screenings, such as mammograms, colonoscopies, diabetes screenings, and many more.

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$121 billion

That's how much Medicare's Part D prescription drug coverage paid for drugs in 2014, up a whopping 17% over 2013's $104 billion. We individuals often pay shocking sums for our medications, but Medicare pays a lot, too. The three drugs that Medicare spent the most on were Sovaldi, Nexium, and Crestor (respectively treating hepatitis C, acid reflux, and high cholesterol), each costing it more than $2.5 billion.

$632 billion

That's how much Medicare benefit payments totaled in 2015. That's also more than the gross domestic product (GDP) of Argentina and more than the recent total market value of Apple.

15%

In 2015, Medicare spending made up a remarkable 15% of the federal budget. It also accounted for 20% of all health spending in America in 2014, as well as 29% of prescription drug retail sales, 26% of hospital care expenses, and 23% of physician services costs.

It's worth learning more about Medicare, in order to be able to make the most of it. And while you're at it, learn more about its cousin Social Security, too. Each has a lot to offer you in your golden years.

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