State officials say a Greece-style financial crisis is a complete nonissue for them, and the bond markets so far seem to agree. All 50 states have investment-grade credit ratings, with California the lowest, and even California is still considered “average,” according to Moody’s Investors Service. The last state that defaulted on its bonds, Arkansas, did so during the Great Depression.

Goldman Sachs, in a research report last week, acknowledged the pension issue but concluded the states were very unlikely to default on their debt and noted the states had 30 years to close pension shortfalls.

Even though about $5 billion of municipal bonds are in default today, the vast majority were issued by small local authorities in boom-and-bust locations like Florida, said Matt Fabian, managing director of Municipal Market Advisors, an independent consulting firm. The issuers raised money to pay for projects like sewer connections and new roads in subdivisions that collapsed in the subprime mortgage disaster.

The states, he said, are different. They learned a lesson from New York City, which got into trouble in the 1970s by financing its operations with short-term debt that had to be rolled over again and again. When investors suddenly lost confidence, New York was left empty-handed. To keep that from happening again, Mr. Fabian said, most states require short-term debt to be fully repaid the same year it is issued.

Some states have taken even more forceful measures to build creditor confidence. New York State has a trustee that intercepts tax revenues and makes some bond payments before the state can get to the money. California has a “continuous appropriation” for debt payments, so bondholders know they will get their interest even when the budget is hamstrung.

The states can also take refuge in America’s federalist system. Thus, if California were to get into hot water, it could seek assistance in Washington, and probably come away with some funds. Already, the federal government is spending hundreds of millions helping the states issue their bonds.

Professor Rogoff, who has spent most of his career studying global debt crises, has combed through several centuries’ worth of records with a fellow economist, Carmen M. Reinhart of the University of Maryland, looking for signs that a country was about to default.