U.S. stock indexes on Wednesday opened sharply lower on the first trading day of 2019, amid mounting concerns about a slowdown in China's economy, which could ripple internationally. The Dow Jones Industrial Average DJIA, +0.13% declined 354 points, or 1.5%, at 22,972, the S&P 500 index SPX, -0.46% retreated 1.4% at 2,472, while the Nasdaq Composite Index COMP, -1.25% fell 1.6% at 6,526. The China Caixin manufacturing purchasing managers index fell to 49.7 in December, marking the first time the sector has been in contraction territory since May 2017. A reading below 50 signals worsening conditions. The retrenchment in the world's second-largest economy comes as Beijing and Washington remain locked in a protracted dispute on tariffs that threatens to unhinge global economies. The S&P 500 was 14.5% short of its Aug. 20 peak, and the Dow was off 13% from its recent high on Oct. 3. The Nasdaq, which is in a bear market, defined usually as a decline of at least 20% from a recent peak, was currently off by about 18% from its apex. Markets were closed on Tuesday for New Year's Day. In corporate news, shares of Tesla Inc. TSLA, -1.77% were sinking after deliveries for the electric car maker increased 8% from a year ago to 90,700, but below the FactSet consensus of 92,000.