Here's how much your health insurance premiums could go up if the tax bill passes

CBO: Average premiums up 20% in 2018
CBO: Average premiums up 20% in 2018

Obamacare's individual mandate is not the most popular aspect of the Affordable Care Act. But as Congress moves toward repealing the mandate as part of tax reform, voters, legislators and industry experts have flocked to its defense, pointing out that doing away with it would cause already high premiums for individual health plans to rise by 10 percent.

As a result, "a coalition of physician, hospital and health insurance industry associations called on Congress [earlier this fall] to keep the individual mandate," reports CNN.

They warned repeal would lead to "a significant increase in premiums" for those seeking to buy insurance on Obamacare marketplaces, which offer coverage to those who don't have insurance through an employer or elsewhere.

That increase would add about $1,000 to the annual cost of coverage for an individual health plan for the average unsubsidized family shopping for coverage via government exchanges. (The Kaiser Family Foundation breaks down which lower- and moderate-income families qualify for subsidies here.) That family would go from paying about $10,000 a year on premiums alone, which is what it spent in 2016, to about $11,000. The average unsubsidized individual, meanwhile, would go from paying about $3,800 a year on premiums to about $4,180.

And the Center for American Progress, which crunched the numbers before the House and the Senate reconciled their bills, warned that the forecast could be even more dire: "A typical middle-class family buying individual market insurance would see premiums increase nearly $2,000."

Increased costs would also threaten the health insurance of about 13 million Americans, according to estimates from the non-partisan Congressional Budget Office.

The definitive guide to retirement savings plans
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The individual mandate requires most Americans to have some form of health insurance coverage or pay a fine. The projected premium increases expected to result from repeal would stem from having fewer young and healthy customers in Obamacare plans, which would have to raise prices to cover health expenses for older, sicker customers.

As it is, Americans pay vastly more for health insurance than citizens of all other advanced countries in exchange for inferior results. As Dan Mangan reports for CNBC, "despite spending well in excess of the rate of any other of those countries in 2013, the United States achieved worse outcomes when it comes to rates of chronic conditions, obesity and infant mortality."

This past summer, when Congress considered ditching the individual mandate as part of a "skinny repeal" — an effort that ultimately failed — the CEO of America's Health Insurance Plans cautioned Senate Majority Leader Mitch McConnell and Minority Leader Chuck Schumer that, should the mandate go, "premiums will rise rapidly, few or no affordable coverage options will be available and more people will be uninsured."

The letter also says that the AHIP would "oppose an approach that eliminates the individual requirement, does not offer alternative continuous coverage provisions, and does not include measures to immediately stabilize the individual market."

The CBO concurred, predicting that skinny repeal would boost the number of uninsured Americans by 16 million and raise premiums by 20 percent as soon as next year and then 10 percent by 2019.

Some Republicans at the time agreed that repealing the individual mandate would leave the marketplace in shambles. "I cannot tolerate our skinny bill being the final answer on health care," said South Carolina Senator Lindsey Graham. "No way. If you passed it as a standalone proposition it would destroy the insurance markets and we would own the failure of Obamacare."

Kaiser Health News pointed out that three individual states have tried versions of a skinny repeal. The results were bleak: "Premiums rose and insurers fled, leaving consumers who buy their own coverage, because they don't get it through their jobs, with fewer choices and higher prices."

The CBO also warned that, under the original Senate Obamacare replacement plan, average deductibles could reach $13,000 or more a year within ten years.

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