Even in the rich world, death from infection still looms; MRSA alone kills thousands every year. And firms are not developing antibiotics as fast as they used to. According to the Infectious Diseases Society of America (IDSA), between 1983 and 1987, the FDA approved 16 new antibacterial drugs for use in humans; from 2003 to 2007, it approved six.

Whom to blame for all of this depends on whom you ask. Patients, physicians, hospitals, drug companies, and even regulators have all taken their turn in the dock. But to an economist, when it’s everyone’s fault, it’s really no one’s fault: what we’re witnessing is not a personal failure, but a market failure.

Almost no one develops something like MRSA in his or her own body. Resistance arises over generations of treatment, usually in hospitals with lots of patients. Though resistance is ultimately inevitable, we can slow its emergence considerably. However, doing so requires strict compliance with tedious and often expensive protocols. Each slip contributes only slightly to the problem, so there’s a high temptation to free-ride: Just this once, I’ll skip washing my hands between patients, or Just today, I’ll skip taking the last of the pills that upset my tummy. Anyone who lived in a group house in college knows how this story turns out.

Markets and property rights give people incentives to avert the tragedy of the commons, and have yielded a steady stream of life-saving drugs and medical innovations. But antibiotics are different from most of the other drugs we use. As Kevin Outterson, a professor of health law and bioethics at Boston University, points out, 100 million people could be taking Lipitor and it would remain just as effective as the day it was first invented. Unless we discover something even better, patients could still be taking Lipitor 1,000 years from now. But antibiotics like penicillin inevitably begin to lose effectiveness.

Antibiotics are an exhaustible resource. We should be treating them like an oil field, or an endangered species. Instead, we handle them like consumer electronics. The patent system is designed to promote human invention, not conserve what has already been discovered. Patents are limited to 20 years, so that other inventors can build on earlier innovations. Arthur Daemmrich, a professor at Harvard Business School who studies the pharmaceutical industry, points out that the pharmaceutical patent life is actually much shorter, because the patent clock begins running before the start of multi-year clinical trials necessary to get the drug approved. And when companies finally get to market, they face the risk that a competitor will be close behind with a related drug. As Laxminarayan says, “The pharma companies don’t have an incentive to conserve the effectiveness of their antibiotics. They have [intellectual-property] rights on a drug, but someone else could be developing a similar molecule that will create resistance to my molecule, so I need to sell it as fast as I can.”