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.
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.
Continue the Trail
We've been building a growing collection of practical investing resources at Unbridled Nation to help make the stock market easier to understand—without burying the Trail Boss in Wall Street jargon.
Explore our new Investing pages:
Unbridled Nation Investing:
Explore the Investing Library
Inside the growing library, you'll find our research into ETFs, individual companies, retirement investing, dividends, market behavior, and the tools we're developing to help separate long-term opportunities from short-term market noise.
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.
The Trail Boss Investing Journey
Our part of a larger ecosystem built around learning, documenting the work, and building something we own. Follow the journey at Unbridled Nation and visit the Unbridled Investing Journey for our growing collection of ETF and stock research.
Start with Saddle Up — Opening Your Robinhood Account, then explore our VOO Composition Record, VOOG Composition Record, VOOV Composition Record, JEPQ research, SPYI research, QQQI research, ORC research, ARR research, NLY research, and IBIT research.
You can also follow the weekly ARDL Bull Weekly model and hear the research unfold on Trail Boss Radio.
The broader mission continues at Unbridled Tech Academy, where we're building a Trail Boss reference library for the terminology, tools, and lessons behind the journey, while iLyft4U remains the working example of the digital-business systems we build in public.
Learn the business. Show the work. Build the trail.
Trail Boss Radio — learning the market one trail at a time.
