Shares of health insurers and hospital operators did, in fact, plunge on Friday , including Tenet Healthcare , which fell almost 5 percent, and Molina Healthcare , which dropped more than 4 percent.

The White House announced on Thursday evening that the administration would immediately halt payments to insurance companies that sell Obamacare plans. As CNBC reported , the move is predicted to sharply increase premiums and may cause affected insurers to exit the marketplace.

President Donald Trump took to Twitter Saturday in triumph over falling health insurance stocks which, he notes, "which went through the roof during the Obamacare years."

President Donald Trump smiles after signing an Executive Order regarding health insurance plans at the White House in Washington, October 12, 2017.

The payments are worth approximately $7 billion to insurers this year and as much as $10 billion, or more, in 2018. They reimburse insurers for discounts in out-of-pocket costs granted to low-income Obamacare customers, and are required by law.

In August, the Congressional Budget Office estimated that premiums for individual plans would rise by about 20 percent if payments if payments stopped. CBO projections also indicate that such a move would push premiums 25 percent higher by 2020 than they would otherwise be and that the federal deficit could increase by nearly $200 billion.

Trump also tweeted pride on Saturday over an executive order he signed Thursday morning, which he says "will allow greatly expanded access and far lower costs for HealthCare."

TWEET

The executive order eases the rules that govern health care plans offered by small businesses, as well the rules surrounding enrollment in short-term health insurance plans, which are less costly and comprehensive than plans offered under Obamacare.

"With these actions," Trump said, during the signing ceremony at the White House, "we are moving toward lower costs and more options in the health-care market, and taking crucial steps toward saving the American people from the nightmare of Obamacare."

It's unclear whether the order will have any serious impact on the U.S. health insurance system before Obamacare's open enrollment season begins in November.