Over the past decade, U.S. Treasury debt has ballooned:

* In 2001, the total was under $6 trillion.

* In 2007, the total was over $9 trillion.

* In 2011, the total is over $14 trillion.

Thus, the national debt has more than doubled in 10 years.

That increase has raised some doubts about the federal government’s ability to repay the principal and interest on that debt. Normally, an issuer in that situation has to increase the interest rate it pays in order to attract skeptical investors.

That hasn’t been the case with Treasuries. Since 2001, the interest rate on 10-year Treasuries has actually declined, from around 5 percent to today’s level of about 2 percent.

The low interest rate means that investors from around the world still want to own Treasuries, even if they have to accept low yields. If sophisticated investors are not worried about a default, you probably can own Treasuries with confidence you’ll be repaid. However, yields are so low that you probably will not want to load your portfolio with Treasury issues. Instead, look for a well-diversified corporate bond fund or municipal bond fund for higher yields.