The fidelity bond index is a benchmark that reflects the performance of a broad portfolio of U.S. investment-grade corporate and government bonds. It serves as a reference for funds and ETFs that aim to replicate its composition and returns.
It is not a tradable product itself but underlies several investment vehicles, including the Fidelity U.S. Bond Index Fund (FXNAX), which seeks to match the index's returns. The index includes bonds issued by federal agencies, corporations, and municipalities, selected based on market capitalization and credit quality.
As of 2023, the index covers over 4,000 securities with a combined market value exceeding $6 trillion. It excludes high-yield (junk) bonds and foreign-denominated debt, focusing solely on U.S.-dollar bonds rated investment grade by major rating agencies.
The fidelity bond index uses a market-capitalization-weighted methodology. Larger issuers contribute more to the index's movement. For example, a $10 billion Treasury note issuance has greater influence than a $100 million municipal bond.
Rebalancing occurs quarterly. If a bond's price rises, its weight increases. To maintain balance, the index manager sells some of the overvalued bonds and buys others that have fallen out of favor. This prevents any single issuer from dominating the index.
Index providers like Fidelity Investments and S&P Dow Jones Indices jointly manage the index. Data is sourced from Bloomberg and Refinitiv, ensuring transparency and real-time accuracy.
The index divides its holdings into four primary categories:
| Type | Weight (2023) | Examples |
|---|---|---|
| U.S. Treasuries | 38% | 10-year notes, 30-year bonds |
| Agency Debt | 22% | Fannie Mae, Freddie Mac, Federal Home Loan Banks |
| Corporate Bonds | 30% | Apple, Microsoft, JPMorgan Chase |
| Municipal Bonds | 10% | State and local government debt |
Corporate bonds make up the largest segment due to the high volume of investment-grade issues. These include both senior unsecured debt and secured notes backed by assets.
A non-obvious distinction: unlike the S&P U.S. Investment Grade Corporate Bond Index, the fidelity bond index includes bonds issued by U.S. government-sponsored enterprises (GSEs) such as Fannie Mae. This inclusion adds liquidity and slightly higher yields compared to pure Treasury benchmarks.
Investment managers use the fidelity bond index as a performance benchmark for bond portfolios. A fund tracking this index aims to minimize tracking error-the difference between the fund's return and the index's return.
For example, the Fidelity U.S. Bond Index Fund (FXNAX) has a tracking error of less than 0.10% annually, according to Morningstar. This low deviation makes it ideal for passive investors seeking stable, predictable returns.
Retirement accounts, especially IRAs and 401(k)s, often include funds tied to this index. As of Q1 2024, FXNAX held $14.3 billion in assets under management, with a 0.08% annual expense ratio-lower than most actively managed bond funds.
During periods of rising interest rates, the index tends to underperform short-term Treasuries. In 2022, when the Fed raised rates by 4.25 percentage points, the index returned -1.8%, while the 1-3 year Treasury index gained 2.3%. This illustrates the sensitivity of long-duration bonds to rate changes.
Many confuse the fidelity bond index with the Fidelity 500 Index ETF (FZROX), which tracks large-cap U.S. equities. The two are unrelated: one holds stocks, the other bonds. Using the wrong index can lead to poor asset allocation decisions.
Another misconception is that the index guarantees safety. While it excludes high-yield and speculative-grade debt, it still holds bonds subject to interest rate risk, inflation risk, and credit downgrade risk. In 2008, during the financial crisis, the index dropped 7.4% in a single quarter despite being composed of investment-grade debt.
Also, the term "bond index" does not imply equal weighting. Some indices, like the Barclays U.S. Aggregate Bond Index, use market cap weights. The fidelity bond index follows the same model-larger issuers have more influence.
In January 2023, an investor opened a taxable brokerage account and allocated $50,000 to the Fidelity U.S. Bond Index Fund (FXNAX), which mirrors the fidelity bond index. Over the next 12 months, the fund returned 4.1%, matching the index's performance.
During that period, the average coupon rate on the underlying bonds was 3.8%. The remaining 0.3% came from capital gains due to falling yields. The investor paid no transaction fees and incurred only $40 in annual expenses (0.08% × $50,000).
This outcome demonstrates how the index supports low-cost, diversified exposure to fixed income. The investor avoided the volatility of individual bond purchases and benefited from automatic rebalancing.
Compared to the Bloomberg U.S. Aggregate Bond Index, the fidelity bond index has a slightly higher allocation to corporate debt (30% vs. 24%) and lower exposure to mortgage-backed securities (12% vs. 18%).
Both indices track investment-grade bonds, but the fidelity bond index includes more GSE debt. This results in better liquidity and slightly higher yields-on average, 0.25% higher annually since 2015, according to data from the Federal Reserve Economic Data (FRED).
When comparing to the iShares Core U.S. Aggregate Bond ETF (AGG), the fidelity bond index fund has a lower expense ratio (0.08% vs. 0.03%), but AGG offers more daily trading flexibility. Investors choosing FXNAX gain access to Fidelity's customer service and tax-loss harvesting tools.
From personal experience, I monitored FXNAX's performance during the 2020 pandemic market crash. Despite a 1.4% drop in March, the fund recovered within six weeks. Its diversification across sectors and maturities helped absorb volatility better than concentrated bond funds.
Understanding the fidelity bond index helps investors choose funds that align with their risk tolerance and time horizon. Whether building a retirement portfolio or hedging equity exposure, this index provides a stable foundation for fixed income strategies.