The mortgage market has been roiled by a sharp increase in bad loans made to borrowers with weak credit. Now there are signs that the pain is spreading upward, the Wall Street Journal reports.

At issue are mortgages made to people who fall in the gray area between “prime” (borrowers considered the best credit risks) and “subprime” (borrowers considered the greatest credit risks). A record $400 billion of these midlevel loans — which are known in the industry as “Alt-A” mortgages — were originated last year, up from $85 billion in 2003, according to Inside Mortgage Finance, a trade publication. Alt-A loans accounted for roughly 16% of mortgage originations last year and subprime loans an additional 24%.

The catch-all Alt-A category includes many of the innovative products that helped fuel the housing boom, such as mortgages that carry little, if any, documentation of income or assets, and so-called option adjustable-rate mortgages, which give borrowers multiple payment choices but can lead to a rising loan balance. Loans taken by investors buying homes they don’t plan to occupy themselves can also fall into the Alt-A category.

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