Tariffs are another wild card. The market has gotten more volatile since the Trump administration began slapping tariffs on imports from various trading partners, especially in its conflict with China. The threats and retaliations, all an effort to get China to the negotiating table, have been turning up the heat since the spring with seemingly no end in sight.
China's economy is cooling down, and that might mean lowering expectations across the board, said Jack Ablin, the chief investment officer at Cresset Wealth Advisors. "We can't keep living in an economic dreamland," he said. "The world's second-largest economy is slowing down, and China's leader wants to deliver. I don't see recession but just have to ratchet down the projections."
— Jeff Cox, Kate Rooney and Thomas Franck contributed reporting.
WATCH: Trade war latest spooks markets