Renewed concerns about Europe's debt crisis led to tremendous upheavel in the U.S. bond market during the week of May 14-18. Worries that the crisis had moved past the point where governments could stop the spread of "contagion" from Greece and Spain to the rest of the Continent caused investors to stampede out of higher-risk assets and into the relative safety of U.S. Treasuries. The yield on the 10-year note fell from 1.84% to 1.70% on the week (as its price rose), bringing it just a shade above its low of 1.696% set in late September. The largest Treasury-focused exchange-traded fund (ETF), iShares Trust Barclays 20+ Year Treasury Bond Fund (ticker:TLT), rose 2.0% on the week.

Meanwhile, the higher-risk segments of the market - which had held up relatively well into this week - finally gave into the pressure of falling stock prices. Corporate bonds slid 1.2%, as measured by the iShares iBoxx $ InvesTop Investment Grade Corporate Bond ETF (LQD), while high-yield bonds fell 3.6%, as gauged by the iShares iBoxx $ High Yield Corporate Bond ETF (HYG). Emerging market bonds also lost ground, with the Wisdom Tree Emerging Markets Local Debt ETF (ELD) dropping 3.0%. This marks the most protracted sell-off for high yield and emerging market bonds since November, 2011.

This is the third year in a row that concerns about Europe have led to a downturn in higher-risk assets in the warm weather months. In each of the past two years, investors moved past their fears within a few months, leading to a recovery in market segments such as high yield and emerging debt. Watch the news out of Europe carefully in the weeks ahead to see if the fears will in fact prove well-founded this time around.

Mutual funds can cost investors money in two ways. The first is the load, which is the upfront sales commission you pay when you buy a fund through a broker. The second is the expense ratio, which is the fee charged by the fund company that offers the product. This fee comes out of the fund assets a little bit at a time, so it's easy to overlook it. Over time, however, it can lead to a significant cost for investors. In this article, the author - Tom DeLegge of ETFGuide.com - takes a look at how much of a fund's annual income is lost to fees. The answer may surprise you: the total expense can range from 11-17% of your fund income. And with yields so low, this percentage may be set to rise even higher.

Learn More:

Why Invest in the Lowest-Cost Mutual Funds?

Why Choose a Bond Index Fund?

Few segments of the financial markets spark more negative commentary than U.S. Treasuries. With yields near record lows - the 10-year note closed Friday at 1.84%, not far from its September closing low of 1.72% - the conventional wisdom is that yields will have nowhere to go but up once the day finally comes for the U.S. Federal Reserve to start raising interest rates from their current levels near zero. With this in mind, we present a point-counter point on the Treasury market.

First, the bad news: columnist Daniel Putnam of InvestorPlace provides no fewer than eight reasons why Treasuries are a bad buy right now. See his article here.

On the other side of the debate is Jonathan Burton of CBS Marketwatch, who presents the views of two investors who still believe there's plenty of time for investors to make money in Treasuries. Click here to read more.

Is it possible yields could just stay near these low levels indefinitely? Absolutely: Japan's real estate bubble began to pop in the early 1990s, forcing its central bank to cut rates near zero - just as the Fed is doing right now. Today, Japanese bonds still yield in the low 1% range, confounding investors who thought that the market would eventually crumble, driving prices down and yields up. Could the same thing happen here?

Emerging market bonds have delivered a stellar return year-to-date through May 11, rising 5.82% as measured by the JP Morgan EMBI+ Index. For most of the year, emerging market debt has been second only to high yield bonds in terms of its performance results. And with good reason: at a time of steady economic growth and improving government finances in the emerging markets, investors have felt that the higher yields available in the asset class more than compensated them for the risks. Emerging markets have also performed very well over the longer term as well, delivering average annual total returns of 14.77%, 8.44%, and 10.57% in the three-, five-, and ten- year periods ended on April 30, 2012, as measured by the JP Morgan EMI Global Diversified Index.

What countries have driven the performance of the EMBI+ on a year-to-date basis? A look at the results show that the returns have been consistent and broad-based:

• Argentina: -2.70%
• Brazil: 3.58%
• Bulgaria: 3.77%
• Colombia: 4.63%
• Ecuador: 4.60%
• Indonesia: 2.84%
• Mexico: 3.38%
• Panama: 5.49%
• Peru: 7.39%
• Philippines: 4.65%
• Russia: 5.59%
• South Africa: 3.79%
• Turkey:7.19%
• Ukraine: 6.73%
• Venezuela: 19.82%

Learn more about the emerging markets:

Introduction to emerging market bonds

How do I invest in emerging market corporate bonds?