The bottom line: The stock market's volatility at the end of 2018 was to a certain degree based in genuinely unexpected fourth-quarter weakness. And 2019 is getting off to a very rocky start. With expected earnings still at or near all-time highs, there's definitely a lot of room for them to be re-rated downwards.
JPMorganis a good example. It had a record year in 2018, earning $32.5 billion in total. That shattered the previous record by some $8 billion. And yet its quarterly fixed-income trading revenue was its worst since the financial crisis.