4. China

You know who has racked up even more debt than hopeful 20-something ceramics-studies grads in the United States? Here’s a hint: It’s a not-exactly-Communist country in Asia that has been on such a wild debt-fueled building spree that it somehow used more cement in just three years earlier this decade than the United States did in the entire 20th century. Think about that. Now think about it some more. Over the past decade, China devoted mountains of cash to build airports, factories and entire would-be cities — now known as “ghost” cities, since the cities are populated by largely empty skyscrapers and apartment towers — all in the name of economic growth. And grow it did.

The result is a country with a supersized population (1.4 billion people) and supersized debt. Where things go from here is anyone’s guess. Optimists might argue that those trillions bought a 21st-century Asian equivalent of the American dream. Pessimists describe that massive debt as a “mountain,” a “horror movie,” a “bomb” and a “treadmill to hell,” all in the same Bloomberg article. One thing seems certain, though: If the so-called “debt bomb” in China explodes, it’s likely to sprinkle the global economy with ash. And with President Trump teasing a trade war that already seems to be threatening China’s massive, export-based economy, we may have our answer soon.

3. The End of Easy Money

Say you lived in the suburbs, and one day your neighbor suddenly pulled up her driveway in a new $75,000 Cadillac Escalade. A week later, she was tugging a new speedboat. A few weeks after that, it was Jet Skis. You might either think, “Wow, she’s rolling in it,” or “Golly, she hates glaciers.” (Hatred of glaciers may prove, actually, to be the real spark of the financial end times.) But what if it turned out that she bought all of those carbon-dioxide-spewing toys on credit, at crazy-low interest rates? And what if those rates suddenly started to spike? The result would likely be good news for the polar ice caps and bad news for her, when the repo man (not to cave to gender stereotypes about repo-persons) came calling.

O.K., overstretched metaphor alert: The “neighbor” is us. Ever since the Federal Reserve started printing money in the name of “quantitative easing” to pull us out of the last financial crisis, money has been cheap, and seemingly any American with a pulse and a credit line has been able to fake “rich” by bingeing on all sorts of indulgences — real estate (despite tighter lending standards), fancy watches and awesome gaming systems, to say nothing of the debt that corporations were racking up, which some market analysts think might be the biggest threat of all.

The problem is: The whole system is now running in reverse. The Fed has been hiking rates and spooking markets in order to stave off inflation and other potential ills. Is this an overdue fit of fiscal sanity, or the equivalent of taking away the punch bowl just as the party was getting started, then dumping it on our heads?