The Federal Reserve's decision to keep interest rates unchanged triggered an unusual steepening of the US Treasury yield curve, with long-term yields surging while short-term yields fell. Investors questioned the Fed's commitment to fighting inflation, pushing the 30-year Treasury yield to a 19-year high. Markets now await the US July payrolls report for clues on the Fed's next policy move.

"You're dealing with the Fed that the market is still trying to understand," JP Morgan's Alex Wolf tells Fortune.

US 30-year Treasury yield hits 5.27%, the highest since 2007. Fed pause in next three meetings at 42.5% YES.

US 30-year Treasury yield hits highest level since 2007. Fed pause in next three decisions at 41.5% YES.