The NHS is collapsing. Patients routinely face treatment delays, overcrowded hospitals, and doctor shortages. Even its most ardent defenders admit that the NHS is in crisis.

Yet American progressives want to import this disastrous model. About one in three Democratic senators and more than half of Democratic representatives support single-payer health care.

Why? The British experiment with socialized medicine has been a monumental failure. It would be foolish to repeat that mistake here.

Single-payer is fundamentally flawed. It relieves consumers of any obligation to pay for their care, at least directly. If the price of care is zero, then every patient can demand an infinite amount. The supply of care, meanwhile, is limited. And the amount of money the government can spend on health care is finite.

In a functional market, patients would demand care and providers would furnish it at mutually agreeable prices. If prices were too high, patients would demand less care, and marginal providers would exit the market. If prices were too low, patients would demand more care, and new providers would enter the market to supply it.

These basic market-clearing principles cannot operate in a single-payer system. Governments must forcibly cap demand at whatever level they’re willing to supply—that is, to pay for it.

The NHS experienced these problems from the start. In its first year, the service went well over its budget. Prime Minister Clement Attlee even begged citizens not to overuse health services. Staff shortages, caused in part by low pay, have plagued the system for decades. The NHS started recruiting doctors en masse from India, Pakistan, and Sri Lanka in the 1960s to address the issue.

Nevertheless, shortages persist. One in 11 NHS posts is currently vacant. Four in five NHS staff worry that these vacancies jeopardize patient safety. The NHS has among the lowest amount of doctors, nurses, and hospital beds than any country in the Western world on a per-capita basis, according to a report from the King’s Fund.

Simply put, the NHS is unequipped to care for its citizens.

A simple influenza outbreak last winter plunged the system into chaos. The NHS canceled 50,000 non-emergency surgeries to make room for an influx of people with the flu. Still, nearly one in five patients had to wait more than four hours in the emergency room.

Such nightmares have grown routine. The British Medical Association recently reported that the NHS now faces a year-round crisis, with waiting times and hospital bed shortages at record levels. An NHS Improvement survey of data from the first three months of 2018 found that 2,600 patients had waited more than a year for elective treatment—a nearly 75% increase from the previous year. It’s no wonder that about 10% of Britons hold private insurance coverage. They simply can’t count on the NHS to deliver quality care in a timely fashion.

The NHS’s supporters claim that the system just needs more money. That was the rallying cry for thousands of Britons who took to the streets this past February and again in late June.

But the British government doesn’t have unlimited resources. More funding for the NHS would require raising taxes. And Britain’s tax burden is already the highest it’s been in 20 years, according to the Adam Smith Institute.

Further, funding for the NHS is already at record levels. It’s projected to grow an average of 1.2% percent per year through 2020-21, to an annual tab of nearly $170 billion. Overall, government spending on health care has surged from about $340 per person in 1950 to $2,985 per person today.

Despite the crisis in the U.K., some Americans continue to be entranced by single-payer. The Democratic Party’s newest superstar, New York congressional candidate Alexandria Ocasio-Cortez, made her support for universal government health care a cornerstone of her campaign. Rep. Keith Ellison, the Democratic National Committee’s second-in-command, recently led a three-day strategy session in Minnesota on how to push for single-payer.

American health care has its problems. But the NHS offers 70 years of evidence that single-payer will not solve them.

Sally C. Pipes is the president, CEO, and Thomas W. Smith fellow in health care policy at the Pacific Research Institute. Her latest book is The False Promise of Single-Payer Health Care. Follow her on Twitter @sallypipes.