$2 trillion debt boom leaves emerging-market companies, and banks, at risk at the first sign of trouble.

Debt worldwide has increased more than 40 percent since 2007, according to Bank for International Settlements.

Debt worldwide has increased more than 40 percent since 2007, according to Bank for International Settlements.

As investors pile in in search of yield, bonds sensitivity to rate changes jumps.

As investors pile in in search of yield, bonds sensitivity to rate changes jumps.

Notes would be written down to zero if banks core equity ratio falls to 7%.

Notes would be written down to zero if banks core equity ratio falls to 7%.

As banks cut loans, companies tap the bond markets if they're able to.