The rally in bond prices, which move in the opposite direction from yields, has helped keep borrowing costs low for companies, municipalities and the federal government. And, along with an unemployment rate at 50-year lows, the stock market’s surge is supporting spending by consumers, who are the main driver of growth in the American economy.

Not everyone benefits when markets rise like this. Some investors bet on certain markets to fall, either because they think they are due for a drop or because they expect that the traditional relationships among different assets — where some go up so others go down — will help them hedge their portfolios.

(And we should note that not absolutely everything rose in 2019: Natural gas was a losing bet. So was cobalt. And even a rising stock market contains more than a few sinking ships. Macy’s, for instance, dropped more than 40 percent.)

There’s little reason to assume that these kinds of uniform gains will continue. Usually, different investments are driven by different kinds of dynamics: Stock prices, for example, have climbed at a faster clip than expectations for profit growth. That means the market is looking more and more overvalued. If corporate profits don’t catch up, stocks could stumble.

And bond markets have soared, but increasing loads of corporate debt could prompt investors to sell if they think these companies are taking on too much risk.

One factor behind the rise in bond prices in 2019 was a growing worry about the impact of the trade war. Even though the trade war isn’t over, Washington and Beijing have reduced the tension between them, and the economy isn’t faring as poorly as people had feared. (Good for stocks, but, perhaps, bad for bonds.)

For now, concerns about such market fundamentals seem to be set squarely on the back burner, after the Fed reinvigorated risk-taking in the markets by cutting interest rates three times out of concern that the trade war and a global growth slowdown would drag the United States economy lower.