Major health insurance companies–Blue Cross, Aetna, United, Humana–have decided not to participate in various states in the Obamacare health-insurance exchanges that will be the only place Americans will be able to buy a health insurance plan using the federal subsidies authorized under the Obamacare law.

Under the Patient Protection and Affordable Care Act (AKA Obamacare), every American must buy a health insurance plan that meets minimum government specifications. If a person does not get health insurance through their employer, and is not on Medicaid, they can buy insurance through their home state’s insurance exchange (which, depending on the state, will be run by either the state or federal government).

States will also operate exchanges where small businesses can buy health-insurance plans.

Individuals and families making up to 400 percent of the federal poverty level will qualify for a federal subsidy to help them buy their government-mandated insurance–but only if they buy their insurance on the government-run exchange.

Also under Obamacare, insurance companies are required to take customers with pre-existing health problems and to provide certain services mandated either by the law itself or by regulations issued under the law by the Obama administration–thus driving up the insurance companies’ costs.

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