A study released by Demos, a research and advocacy organization, may shed light on why some working families have credit card debt and others don't.

The study, "Understanding the Debt Difference," is based on survey research of 2,248 low- and middle-income adults between April 2008 and August 2008, and contrasts the demographics, financial habits and economic circumstances of those with credit card debt and those without it.

For survey respondents who met the criteria for the "indebted" group, the average amount owed was $9,799, and 52% said they had the same or more debt than three years before. More than half of the indebted households said they had been late or had missed a credit card payment, and 37% were still paying off a credit card they had cancelled.