The smartest insight and analysis, from all perspectives, rounded up from around the web:

The stock market's "sharp plunges and euphoric rises" in the final weeks of 2018 were nothing short of dizzying, said Jessica Menton at The Wall Street Journal. The end of the year included the "worst-ever Christmas Eve sell-off," followed by a "1,086-point climb in the Dow — the biggest one-day point gain on record — and an 871-point swing Thursday." That comes after a "rough December" in general, and a prolonged falloff over the past three months. U.S. stocks ended the year with their worst annual showing in a decade, and opened 2019 with another day of wild gyrations. That offers a "stark warning that the forces powering the market's seemingly unstoppable rise" are giving way to a much more capricious reality, said Heather Long and Thomas Heath at The Washington Post. The markets are anxiously watching "a partial government shut­down with no end in sight, the losses of key members of Trump's team in public disputes over policy, a presidential threat to shut the border with Mexico, and incessant attacks on the Fed." Mean­while, few analysts expect 2019 to match 2018's strong U.S. economic growth. So the roller-coaster ride is likely to continue.

After nearly two years of stocks "rising relentlessly," the "overriding cause" of shifting markets is "uncertainty about the economy and how much longer the near-record expansion can continue," said John Roper at the Houston Chronicle. But many of the "economic fundamentals" remain strong. Don't forget: "The stock market is at best a minor indicator of the health of the U.S. economy, as only about half of Americans even own stock." Unemployment, at 3.7 percent, is the lowest in 50 years. And consumer spending, which amounts to about 70 percent of U.S. economic activity, has been on an upswing for the past nine months. In fact, 2018's holiday sales increased 5.1 percent to more than $850 billion — "the strongest growth in six years." Wall Street analysts and investors "are still expecting gains next year," said Peter Eavis and Guilbert Gates at The New York Times, "even if they're not quite as boisterous in their predictions as they once were." Stocks could recover next year to their mid-2018 highs, but a lot of things would have to go right, with the Fed treading "a delicate middle ground" on interest rates, the trade war winding down, and the economies of Europe and China stabilizing.

Of course, you can't really talk about the temperamental stock market without mentioning our unpredictable president, said Justin Fox at Bloomberg. "After two years during which things generally went well, and the president claimed credit for it, it is thus only natural to see this month's stock-market sell-off as a referendum on Donald Trump." The truth is, it's much more complicated. There are other factors driving the market's nosedive: tech companies' downward slide, expensive stocks, and plain old herd behavior. The stock market's current storm will probably dissipate. But Trump's behavior during the past month's slump doesn't bode well for "how this president and his shrinking, beleaguered band of aides might react in the face of a real economic downturn."