PHOENIX — A plan that lets Arizona families save for college tuition and earn money on the deposits tax-free has topped $1 billion in assets.

The milestone announced by the state agency that oversees the Arizona Family College Savings 529 program comes just 16 years after it was created.

More than 75,000 accounts are in place allowing parents, grandparents or relatives to contribute to an account set up for a child's college tuition. Earnings are tax-free if used for tuition or other college expenses.

Arizona's plan is sponsored through the Arizona Commission for Postsecondary Education. Executive director April Osborn said in a statement Tuesday that research shows that college with any college savings are six times more likely to attend a four year school.