The biggest buyers of U.S. Treasurys have turned fickle on U.S. debt, just when they may be needed most.
Peter Boockvar, chief market analyst at The Lindsey Group, points out that for a fourth month in a row, foreigners were net sellers of U.S. notes and bonds, dumping $13.1 billion in July for a year-to-date total of $156 billion.
That compares to net selling of $20 billion for all of 2015, but foreigners made massive purchases of about $1 trillion in total for the four years prior to that.
"This level of selling is unprecedented," he said. And it comes just as U.S. interest rates may have seen their cycle lows and bond yields look set to rise.