Americans aren’t suddenly saving a lot more of their incomes. But it looks that way, thanks to a change in how the federal government accounts for pension plans — a change that, if you’re not careful, could lead you to think the nation is better set for retirement than it actually is.

Until Wednesday morning, the Commerce Department pegged America’s personal savings rate at 4.1 percent for 2012. A revision made every five years to how the department measures the components of the economy pushed that savings rate up; now it’s 5.6 percent for 2012. The same change makes savings look much stronger before the Great Recession, too: The rate for 2002 was revised up from 3.5 percent to 5 percent. For 2005, it rose from 1.5 percent to 2.6 percent.

That money isn’t necessarily real. The Bureau of Economic Analysis didn’t find hundreds of billions of dollars stuffed in Americans’ mattresses. It decided to start counting all pension promises as savings in the bank.

That change is called accrual accounting, and as officials at the BEA point out, it’s a well-accepted practice in the corporate world. The idea is that if a company or, more likely in this case, a government entity, has agreed to provide pension benefits to workers, the value of those benefits should count as savings for the worker, even if the company or the government doesn’t have a future income stream large enough to cover all those pension IOUs.

The promises that aren’t backed by an income stream are called unfunded liabilities, and by changing how it counts them, the government added almost $200 billion to the nation’s personal savings for 2012.

The catch is, what if those promises don’t come true? The accounting change was made shortly after Detroit became the largest U.S. city to file for bankruptcy, in part because of the unfunded liabilities in its pension plan, raising questions about whether pensioners will actually receive the benefits they’ve been promised. Signs point to more strains on state and local government pension funds down the road.

There are already signs that analysts are misreading the accounting change and underplaying the possibility that some of the newfound “savings” will never materialize as retirement income.

Economists at Bank of America Merrill Lynch flagged the rising savings rate for recent years in a research note on Wednesday and hailed it as a sign that the economy is stronger than previously thought. “The upward revision to the saving rate was possible even with an upward revision to consumer spending over the past few years,” they wrote. “This shows a healthier household sector and support for future consumer spending.”

The note never mentioned the accounting change.

Still, some economists said it’s unlikely the shift will affect savers’ psychology much.

“The truth is, the accounting of pension assets contributions and assets is always problematic, since they are invested in markets, so their value changes every day,” said Robert Shapiro, who oversaw the BEA as a Commerce undersecretary in the Clinton administration.

He added: “I don’t think the savings rate gives much of a sense of security to anybody – though an artificially high rate may give politicians the reason they need to do less.”