The Dow Jones Industrial Average DJIA, -1.92% late-morning Thursday was trading at its lowest level of the session, as investors reacted to a falling crude-oil prices CLF9 and fresh doubts about the likelihood of a lasting U.S.-China tariff resolution. The Dow was down 720 points, or 2.9%, at 24,319, the S&P 500 index SPX, -2.37% tumbled 2.6% at 2,630, while the Nasdaq Composite Index COMP, -3.01% fell 2.2% at 7,003. Shares of Boeing Co. BA, -3.58% were the biggest drag on the blue-chip Dow, with the index falling about 1,500 points in the past two sessions alone. A combination of factors have led to the recent downturn, the decline in oil is partly being read as a signal that global growth is decelerating and that may impact the U.S. economy eventually. Meanwhile, the 10-year Treasury note TMUBMUSD10Y, 0.675% yield has fallen to 2.84%, and that decline has been narrowing the differential between the benchmark government bond and the 2-year Treasury note TMUBMUSD02Y, 0.144% . A flattening yield curve, as the slope of Treasury yields from shortest to longest is often described, naturally slopes upward because investors tend to demand greater yields for lending for a longer period. A narrowing gap has indicated that investors are worried about the economic outlook in the U.S., with an inversion of that curve--where shorter-dated yields rise above longer-dated ones--serving as an accurate recession predictor.