With interest rates remaining near historic lows and U.S. stock market volatility increasing, now is an opportune time for bond investors to take a closer look at what comprises the core of their fixed income portfolios. Many investors look to core bonds – U.S. investment grade bonds, including corporate, mortgage-backed, Treasury and agency debt – as a portfolio stabilizer and reliable source of income.
A popular approach to gaining this fixed income exposure is to invest in a passive index strategy designed to track the Bloomberg Barclays US Aggregate Bond Index (the Agg). While more than 35 years of falling rates have benefitted indexed and active fixed income investors alike, active core and core plus strategies have outperformed.1 Notably, the index itself has quietly morphed since the financial crisis, resulting in a different go-forward exposure profile. As the rate environment evolves, the index’s changes may become more evident, and investors holding a passive Agg strategy are likely to find their portfolio behaving differently than it had in the past.
The US Agg has changed
The Bloomberg Barclays US Aggregate Bond Index – simply referred to as “the Agg” – has a long history and is solidly entrenched as a benchmark for fixed income performance. But, that doesn’t mean it can – or should – be viewed as a proxy for a holistic, well-diversified bond portfolio going forward.
In fact, several factors have altered the Agg’s risk-return profile, which could present implications for passive bond investors:
The index’s allocation is based on the amount of debt an issuer has, so the most indebted borrowers receive the highest weighting in the Agg.
Post financial crisis, the characteristics of the Agg have changed materially, and we expect these changes to continue. Today, the index is more concentrated in US Treasuries, less diversified across sectors and more sensitive to a rise in interest rates.
Given the Agg’s current low yield and higher duration, a 50 basis point increase in yield could wipe out the coupon component of the index’s return. So, a more pronounced increase would likely result in a negative total return.
What does this all mean? The composition of the Agg has become increasingly concentrated in government-related securities (now about two-thirds of the index), straying from the holistic, well-diversified bond portfolio investors assume it to be.
The Agg has access to only half the U.S. market
With the Agg accounting for just 52% of the broader U.S. bond market, a passive core fixed income investor may be missing out on the other half of the opportunities available in the U.S. bond market. An active approach has a broader opportunity set and can navigate around the Agg’s rule-based constraints to seek improved returns, reduced risk and enhanced diversification.
THE COMPOSITION OF THE AGG
Core Bond Fund
Quality at the core. A value-driven approach that emphasizes intermediate bonds of the highest quality, the Fund serves as a foundation for investors seeking a well-diversified portfolio.