FOR the past three months American politicians have been rowing over the disastrous launch of Obamacare’s website, on which people can shop for health insurance. The new online “exchanges”, created under America’s health reforms to provide cheap private care for millions of uninsured people, are so far the most visible element of Obamacare. Once the software glitches are fixed, sellers of private health plans should gain new customers. But in the years ahead they have a far bigger opportunity: as more Americans come to depend on the government to pay for their treatments, more of them will have their publicly funded health care managed in some way by private insurers.

America has two main public health-insurance programmes: Medicare for the old and Medicaid for the poor. As baby-boomers age, the numbers hitting their 65th birthday, and thus qualifying for Medicare, are rising inexorably. As for the poor, another part of the Obamacare reforms will entitle millions of low-income families to join Medicaid for the first time. Add in the effect of a rising population, and the combined enrolments of Medicare and Medicaid will grow by around 30% by 2022, when one-third of the population will be on one scheme or the other.

Since the government also pays for the health care of its own employees, by the early 2020s the taxpayer will be footing the bill for half of America’s health spending, which will have risen to a staggering $5 trillion, equivalent to one-fifth of the country’s entire economic output. American health care will no longer be predominantly funded by private individuals and employers. Yet giant private insurers like UnitedHealth Group, Humana and WellPoint should get bigger.

In theory, patients with ordinary Medicare and Medicaid coverage can turn up at any clinic and ask to be treated, with the bill sent to the government. In practice, many doctors turn them away because the government’s reimbursement rates are too low. And Medicare does not cover the full cost of all treatments, so most patients buy private insurance to cover the gaps.