How US health insurers make money and why medical costs move their shares

Health insurance is one of the largest sectors in the US economy, yet the business model of major players like UnitedHealth Group (UNH) and Elevance Health (ELV) comes down to a simple balancing act. These companies collect recurring monthly premiums from employers, individuals, and the government, and they use that pool of money to pay for doctor visits, surgeries, and prescription drugs.

Because premiums are generally locked in for a year at a time, an insurer’s profit depends heavily on whether its customers use more or less medical care than expected during that twelve-month window. When patients head to the hospital more often than actuaries predicted, insurer profit margins can shrink quickly.

The single most important number: Medical care ratio

When reading an insurance company’s earnings report, the first figure investors look for is the medical care ratio (MCR), sometimes called the medical loss ratio. This percentage measures how much of every premium dollar goes straight toward paying medical claims.

For example, if an insurer reports an MCR of 83%, it means 83 cents of every dollar collected in premiums went to patient care, leaving 17 cents to cover administrative salaries, technology, taxes, and profit. Because health insurers operate on relatively thin net profit margins, even a 1% or 2% rise in the medical care ratio can translate into a substantial drop in earnings per share.

• Commercial plans: Coverage sold to employers or individuals. Insurers often serve as administrators for large companies that pay their own employees’ medical claims, earning a predictable fee per member.
• Medicare Advantage: Private health plans for seniors and people with disabilities, funded by the federal government. These plans have grown rapidly over the past decade, though government reimbursement rates and seniors’ surgical needs can fluctuate.
• Medicaid: State-run programs for lower-income Americans that private insurers manage under government contracts.

Why insurers built massive health services divisions

Under the Affordable Care Act, US health insurers are legally required to spend at least 80% to 85% of their premium revenue on medical care or quality improvements. If they spend less, they must rebate the difference to customers. This rule effectively caps how much profit a company can squeeze out of pure insurance.

To grow earnings beyond those caps, giants like UnitedHealth Group and Elevance Health have built vast health-services arms—most notably UnitedHealth’s Optum and Elevance’s Carelon. These divisions are not bound by insurance profit caps. They operate outpatient surgery centers, employ tens of thousands of doctors, sell data-analytics software to hospitals, and run pharmacy benefit managers (PBMs) that negotiate drug prices between pharmaceutical companies and employers.

What moves health insurance stocks

In the short term, health insurance stocks react sharply to utilization trends. If a wave of seniors decides to catch up on delayed hip and knee replacements, or if a severe flu season drives up emergency room visits, insurers must pay out more claims immediately while waiting until the next calendar year to raise their premium prices.

In the longer term, regulatory changes and government payment updates are the biggest drivers. Every spring, the US government announces baseline payment rates for Medicare Advantage plans for the following year. Because millions of retirees are enrolled in these plans, a generous rate update acts as a tailwind for the industry, while a tight rate update forces insurers to trim supplemental benefits or accept lower margins.

For everyday investors, evaluating a health insurer means watching two things at once: whether the core insurance unit is pricing its policies accurately to cover rising hospital and drug bills, and whether its health-services division is expanding fast enough to provide steady, fee-based cash flow.