With the 10-year anniversary of the onset of the global financial crisis just weeks away, now is a good time to ask where the next global economic crisis might come from. To be clear: We’re not sounding any alarms here. We don’t think a crisis is imminent. But we do like to keep our eyes on the horizon.

Reforms to the global financial system in the wake of the 2008–2009 crisis mean the next crisis probably won’t look like the last one. So what will it look like?

“If you follow the financial news, then you know shocks to the global system happen all the time—and are promptly absorbed by the system without much disruption,” says Schwab chief global investment strategist Jeffrey Kleintop. “Some recent examples could include the recent tensions between the U.S. and North Korea, the U.S. Fed beginning to reverse its quantitative easing program, or the rapid unwinding of the short-volatility trade that took place earlier this year.”

“More concerning are shocks that could have a deeper impact,” he says. “That happens when a shock hits the system and the system isn’t prepared for it. The system is often at its most vulnerable near the end of the global economic cycle, when excesses have built up and managing risks may have been neglected.”

Since we may now be in the later stages of a cycle, let’s review some of the potential sources of vulnerability out there. Here are five:

High debt levels

Since 2001, global debt has nearly tripled. As of 2016—the latest year for which International Monetary Fund data is available—global debt stood at $164 trillion (225% of gross domestic product), up from $62 trillion in 2001 and $116 trillion in 2007, just ahead of the onset of the financial crisis. More than a third of developed economies have debt-to-GDP ratios above 85%, according to the IMF.1 That’s three times worse than 2000.

“While a high debt burden by itself isn’t necessarily a cause for concern, it increases the vulnerability to rising interest rates, particularly with quantitative easing programs—which kept interest rates low—winding down,” says Jeff. “Throw in a strong dollar pushing up the cost of dollar-denominated debt overseas, and the shock from rising interest rates could be costly.”