College student debt (most of it owed directly to the federal government) continues to grow and has now put its grip on almost 20 percent of American households.

A recent study by the Pew Research Center has found that 22.4 million households, or almost 20 percent of American families, had college debt in 2010. That rate is double the share back in 1989, and up from 15 percent in pre-recession 2007. This number of student debtholders represents the biggest three-year increase in student debt in more than two decades.

According to the report, “the debt burden was the greatest for the poorest 20 percent of households, or those making less than $21,044. In all, 40 percent of U.S. households headed by someone younger than age 35 owed college debt, the highest share of any age group.”

The Pew report also noted that the richest 20 percent of households, with annual income of $97,586 or higher, owed the greatest share of outstanding student debt, 31 percent. That is a 3 percent increase since 2007. The student debt among the poorest 20 percent of households grew to 13 percent or up 2 percent since 2007.

See the Associated Press story on the Pew Research Center report here.