Episode Details

The Missing Half of the Bond Market

What if the bond-market benchmark you've been using doesn't actually represent the whole bond market?

In this episode of Trail Boss Radio, we follow the money into the world of bonds and index funds to uncover something many investors may never have considered: the Bloomberg U.S. Aggregate Bond Index—the "Agg"—doesn't represent every corner of the U.S. bond market.

In fact, the research suggests that roughly half of the U.S. bond market falls outside the Agg's rules.

So what exactly are we missing?

We explore how the Agg is constructed, why it focuses on investment-grade, fixed-rate, taxable bonds, and why important areas such as high-yield bonds, municipal bonds, TIPS, and floating-rate securities can fall outside its boundaries.

But this episode goes deeper than simply looking at bonds.

We also examine one of the most interesting questions in passive investing:

Does an index fund actually need to own every security in its benchmark?

That leads us into the difference between full replication and representative sampling.

A full-replication fund attempts to own every security in an index. A sampling fund selects a smaller group designed to behave like the entire index.

At first, sampling sounds like the obvious way to save money.

But the research raises an unexpected finding: for many smaller indexes, sampling can introduce additional trading, higher costs, and poor security selection that can actually hurt long-term returns. The research suggests that sampling funds following indexes with fewer than 1,000 securities have historically underperformed full replicators by roughly 60–70 basis points per year.

That's a small number.

Until you let it compound for decades.

However, the story changes when indexes become extremely large. Once an index contains thousands of securities, completely replicating it can become expensive and difficult. At that scale, sampling may finally become an efficient way to avoid trading tiny, illiquid positions.

That gives us an important Trail Boss lesson:

A strategy that works in one market may not work the same way in another.

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Trail Boss Disclaimer

This podcast is for educational and informational purposes only. It is not financial, investment, tax, or legal advice. Investing involves risk, including the possible loss of principal. Always do your own research and consider consulting a qualified financial professional before making any investment decisions.

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