AFTER A ROTTEN October and limp November, the S&P 500 tumbled in value by 15% between November 30th and December 24th. Despite an astonishing bounce of 5% the day after Christmas, the index finished the year 6% below where it started (see chart). The first trading day of 2019 extended the market wobble, with stocks closing down in Asia and gyrating in Europe. After markets closed in America, Apple warned that a sharp slowdown in China’s economy, and weak sales in other emerging markets, meant revenues in the fourth quarter would undershoot expectations by up to 10%. Coming a day after news that China’s manufacturing sector contracted in December, that spooked investors globally. S&P 500 futures dipped before Wall Street re-opened on January 3rd.