Even in the best of times, hospitals try to figure out how to balance the books while serving a significant number of patients who are unable to pay. And these days, they have to deal with a weak economy and the specter of cuts in government funding in 2013. So it may come as a surprise to some investors that these under-assault health care centers have been among the best-performing investments.

Indeed, municipal bonds issued by hospitals have returned 6 percent in 2012 and 15 percent over the past year, far outpacing the average muni bond's return. Since the gains on many of these bonds are immune to some taxes, their effective returns are even higher. Analysts attribute the great performance to the push by some investors to find higher-yielding investments. Hospital bonds have an average yield of more than 3 percent, compared with about 2 percent for municipal bonds on the whole.

It's all the more perplexing that, in a world in which many people are avoiding certain investments -- particularly stocks -- because they seem too risky, investors are looking at hospitals, whose funding sources are anything but secure. Hospitals are obliged to take patients who can't pay or who can pay only through Medicare or Medicaid, whose rates are set by the government and are often lower than those of private insurers. Health care reform, in nearly any form, promises to squeeze those payments even further, with more than $150 billion in cuts to Medicare reimbursement rates, among other reductions.

Despite all this, investment managers say other factors, from razor-thin Treasury yields to the relatively light supply of hospitals looking to borrow, mean these bonds can pay off. Hospitals and other health care facilities sold $27 billion worth of municipal bond debt in 2011, less than half of what they sold in 2008, according to The Bond Buyer. There's still a nice difference between what a hospital bond will pay and what an average municipal bond of similar credit quality will pay, says Rob Amodeo, comanager of the $5.5 billion Legg Mason Western Asset Managed Municipals fund.

Some pros say bonds from stand-alone hospitals might offer the best bargains. But many experts prefer big multihospital systems, because they have more financial stability and might have an easier time adopting cost-saving technologies such as medical-record and billing software. Becoming more efficient will be a necessity if funding cuts really are in the cards. "The big systems have the scale. They're run like corporations," says Robert DiMella, comanager of the $571 million Mainstay Tax-Free Bond fund. Among the bonds in DiMella's portfolio: 30-year, A+ bonds backed by California's Kaiser Permanente, yielding 5.3 percent, and 26-year, triple-B+ bonds backed by Mountain States Health Alliance, which operates in several Southern states, yielding 4.2 percent.