Bonds enjoyed a massive rally from 1981 until July 2012, but now a sustained decline may have begun, experts tell The Wall Street Journal.

The 10-year Treasury yield has soared to 2.67 percent from 1.66 percent May 2 amid speculation that the Federal Reserve will taper its quantitative easing soon. Some economists say the Fed may reduce its $85 billion of monthly bond purchases as soon as December.

Plenty of investors are vulnerable if bond prices do fall. U.S. taxable-bond funds have assets of $3.8 trillion, more than five times the $720 billion total of 2000, according to Lipper data cited by The Journal.

Editor’s Note: Obama Donor Banned This Message (Shocking)

If bond prices fall, so does the value of those funds

"Investors could be in for a rude awakening" if bonds drop farther, Barry Fennell, a senior Lipper research analyst, tells The Journal.

Given that the Fed has never embarked on such a large quantitative easing program before, it's difficult to know how strongly the market will react to a tapering.

"This is something we haven't been through before," Steve Huber, a bond-fund manager at T. Rowe Price Group, tells The Journal.

To be sure, some experts anticipate that Fed Chairman-nominee Janet Yellen would be stingy about tapering, and that's providing support for bonds.

"Yellen is dovish, and that should underpin demand for Treasurys, although a lot of that has probably been in the price," Nick Stamenkovic, a fixed-income strategist at broker RIA Capital Markets in Edinburgh, tells Bloomberg.

"We expect Treasurys to move in a narrow range in the near term."

Editor’s Note: Obama Donor Banned This Message (Shocking)

Related Stories:

Pimco's Gross: Bond Rally End Unlikely to Be Reminiscent of 1994

Bill Fleckenstein: Bond Market Could Experience 'Train Wreck'