As the global economic rebound tries to gain steam, bond investors may be scratching their heads wondering why they’ve been left behind. Most major assets—including stocks, real estate and commodities—have effortlessly outperformed their fixed-income counterparts.

Two popular fixed-income ETFs—the Vanguard Total Bond Market Index Fund (BND) and the iShares 20+ Year Treasury Bond ETF (TLT)—have slid 0.4% and 3.6% year to date, respectively. Moreover, funds with a foreign flair haven’t done much better. The SPDR Bloomberg Barclays International Treasury Bond ETF (BWX) has declined 4.1%.

While the losses are modest, the performance gap between bond ETFs versus funds in competing asset classes is quite large.

For comparison, the Schwab U.S. Broad Market ETF (SCHB), which covers the entire U.S. stock market, has climbed 18%. Other ETFs that got crushed during last year’s coronavirus crash, for example, the iShares Global REIT ETF (REET) and United States Commodities Index Fund (USCI), have jumped 22.6% and 24.1% this year, respectively.

BND holds investment-grade bonds, which are generally sought by risk-averse investors due to a lower likelihood of default. Bonds with a Baa3 rating from Moody’s or BBB- by Standard & Poor’s can still make the cut as investment-grade quality. With $80.3 billion, BND is the second-largest bond ETF by assets after the $89.2 billion iShares Core U.S. Aggregate Bond ETF (AGG).

TLT holds exposure to U.S. Treasuries with durations of 20 years or longer. After sizzling gains of 14.1% in 2019 and 18.2% in 2020, TLT’s performance has recently cooled off. Rising interest rates been a major factor in the fund’s lackluster showing.

The yield on 30-year Treasuries has inched up to 1.85% from 1.66% at the start of the year. Higher rates have the biggest negative impact on long-term bond prices. TLT has $16.6 billion in assets and charges annual expenses of 0.15%.

Treasury inflation-protected securities, also known as TIPS, and high-yield bonds have been two bright spots in the bond market.

The iShares TIPS Bond ETF (TIP) and the SPDR Bloomberg Barclays High Yield Bond ETF (JNK) have increased 4.3% and 2.8% year to date, respectively.

TIPS are designed to provide protection against inflation as measured by the Consumer Price Index. If inflation is rising, as it is right now, the principal of TIPS will rise. Conversely, the principal of TIPS will decrease during deflationary periods.

In June, the CPI experienced a 5.4% year-over-year jump, which was the largest 12-month increase since August 2008. Surging inflation has boosted the performance of TIPS-focused ETFs. TIP has $31.3 billion in assets and an 0.19% expense ratio.

Over in the high-yield bond market, ETFs that hold bonds with a lower credit quality, such as JNK, have enjoyed better returns against safer investment grade bond funds.

Thus far, the outperformance of TIPS and high-yield bond ETFs in 2021 continues to play out. And while the overall fixed-income market is still a mixed bag, a few bright spots remain.

Ron DeLegge is founder and chief portfolio strategist at ETFguide, and is the author of "Habits Of The Investing Greats."