Kroll Bond Ratings said that growth in the student loan debt market could have future negative impacts on the growth of mortgage debt and auto loan debt. The information came in Kroll’s first quarter 2014 US Consumer Credit Update. Student loans are the largest component of non-mortgage and home equity debt, at $1.111 trillion. uto loans represent the second largest segment of non-mortgage and home equity consumer debt balances, the report says. Both auto and student loan debt have increased over the past few years, after declining during the recession. Today, auto loan debt balances are the highest they have been in the last ten years. Over the past quarter, student loan debt increased by $31 billion and auto loan debt was up by $12 billion.