Matt Phillips:

After the worst of the Great Recession, it didn’t take long for the subprime market to start growing again in the US.
 Subprime auto loans—that is car loans made to people with shaky credit histories—have been growing fast over the last few years. In 2009, about 17% of the auto loans bundled up into bonds known as asset-backed securities (or ABS, similar to the mortgage-backed securities that crashed the financial system) were subprime. By the first quarter of 2014, that figure had swollen to 31%, according to data from Citi analysts.
 And now some of those borrowers are falling behind on payments. Citigroup analysts spotlighted the trend in a recent note—though it’s somewhat strange, they pointed out, as most American households’ balance sheets are currently improving. “The deterioration is quite striking in relation to the 2003–2009 period, when households were relatively worse off,” Citi analysts wrote.