Widely used data on the adequacy of retirement savings based on the Census Bureau’s data may understate how financially secure retirees are, according to the Center for Retirement Research.

In particular, the data does not capture certain information regarding retirement income from employer-sponsored retirement savings plans or from IRAs. For example, while the Census data showed that retirees drew $18 billion of income from such assets in 2012, a report from the Federal Reserve Board puts the figure at $220 billion and the IRS-generated number is $229 billion.

That’s an increasingly important distinction as retirees will increasingly rely on such accounts in the future over defined benefit programs, it said. A conclusion that retiree finances are better than believed could drive decisions on changes in law affecting Social Security and other benefits.

It added, though, that because such assets tend to be concentrated among higher-income households, that’s where the understatement of income largely lies. For middle income and lower income households, the income picture is essentially accurate, it said.