Bond ETFs for Beginners: BND vs AGG vs SGOV — What's the Difference?

Bonds have a reputation for being boring. And in a world where everyone is talking about AI stocks and 30% annual returns, fixed income doesn't exactly dominate the conversation. But bond ETFs serve a real purpose in a portfolio — and in a rate environment where short-term yields are meaningfully positive, they're more interesting than they've been in years.

Whether you're building a balanced portfolio, looking for somewhere to park cash that beats a savings account, or getting closer to retirement, understanding how bond ETFs work — and what BND, AGG, and SGOV actually hold — is worth your time.

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What Is a Bond, and Why Do They Matter?

Before the ETFs, let's make sure the underlying asset makes sense.

A bond is a loan. When you buy a bond, you're lending money to an issuer — typically the U.S. government, a corporation, or a municipality. In exchange, the issuer promises to:

1. Pay you a fixed rate of interest (the coupon) at regular intervals
2. Return your principal at the end of the loan term (maturity)

Bonds are generally less volatile than stocks because the cash flows are contractually fixed. The primary risk in owning bonds is interest rate risk: when rates rise, existing bond prices fall (and vice versa). The longer a bond's maturity, the more sensitive it is to rate changes.

Bond ETFs bundle dozens or hundreds of individual bonds into a single, tradeable fund. Instead of buying one bond and waiting for it to mature, you own a continuously managed portfolio of bonds that generates monthly income and trades on an exchange like any stock.

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The Three Funds: A Quick Overview

| | BND | AGG | SGOV | |---|---|---|---| | Full name | Vanguard Total Bond Market ETF | iShares Core U.S. Aggregate Bond ETF | iShares 0-3 Month Treasury Bond ETF | | Issuer | Vanguard | BlackRock | BlackRock | | Expense ratio | 0.03% | 0.03% | 0.07% | | What it holds | Broad U.S. investment-grade bonds | Broad U.S. investment-grade bonds | Ultra-short U.S. Treasury bills | | Duration | ~6–6.5 years | ~6–6.5 years | <0.25 years | | Yield (approx. 2026) | 4.5–5.0% | 4.5–5.0% | 4.3–4.7% | | Rate sensitivity | Moderate-high | Moderate-high | Essentially none | | Best for | Core fixed-income allocation | Core fixed-income allocation | Cash management, capital preservation |

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BND: Vanguard Total Bond Market ETF

BND tracks the Bloomberg U.S. Aggregate Float Adjusted Index — a broad index of U.S. investment-grade bonds. "Investment-grade" means bonds rated BBB or higher by major rating agencies, indicating low default risk.

Expense ratio: 0.03%

BND holds over 10,000 individual bonds, including:

• U.S. Treasury bonds (~45–50% of the fund) — the safest bonds in the world, backed by the U.S. government
• Mortgage-backed securities (~25–30%) — pools of home mortgages packaged as bonds
• Corporate bonds (~20–25%) — debt issued by large U.S. companies like Apple, Microsoft, and JPMorgan

The fund pays monthly dividends (interest distributions), making it popular for income-oriented investors.

Duration: About 6–6.5 years. This is a key number. Duration measures how much a bond fund's price will change for a 1% change in interest rates. A duration of 6.5 means: if interest rates rise by 1%, BND's price will fall by roughly 6.5%. If rates fall by 1%, the price rises by ~6.5%.

That's why 2022 was painful for bond investors. When the Fed raised rates by over 4 percentage points in roughly 18 months, BND fell roughly 13% — a decline many "safe money" investors weren't prepared for.

Who BND is for: Long-term investors who want a low-cost, diversified fixed-income core holding. Best suited for tax-advantaged accounts (IRAs, 401ks) since bond interest is taxed as ordinary income. Also appropriate for investors using a classic stock/bond split portfolio (60/40 or 80/20).

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AGG: iShares Core U.S. Aggregate Bond ETF

AGG tracks a nearly identical index to BND — the Bloomberg U.S. Aggregate Bond Index. The two funds hold very similar portfolios and have nearly identical returns over any meaningful time horizon.

Expense ratio: 0.03%

The primary differences:

• AGG is issued by BlackRock (iShares), BND by Vanguard
• Slight differences in index methodology lead to minor portfolio variations
• Both hold 10,000+ bonds with similar sector and duration profiles

For all practical purposes, BND and AGG are interchangeable. Your choice should come down to which brokerage you use or which fund has slightly better liquidity for your use case. Both are excellent funds.

Who AGG is for: Same as BND. If you're at a BlackRock-ecosystem brokerage, AGG is your default broad bond fund. At Vanguard, use BND. Either works.

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SGOV: iShares 0-3 Month Treasury Bond ETF

SGOV is a completely different animal from BND and AGG, and understanding the difference is important.

Expense ratio: 0.07%

SGOV holds only U.S. Treasury bills with maturities of 0 to 3 months — the shortest possible government debt. Treasury bills are issued by the U.S. government and backed by the full faith and credit of the federal government. They're widely considered the closest thing to a risk-free asset available.

Duration: Nearly zero. Because the bonds in SGOV mature in less than three months, the fund has almost no interest rate sensitivity. When the Fed raises or cuts rates, SGOV's price barely moves — its yield adjusts almost immediately as old T-bills mature and are replaced by new ones at current rates.

The yield on SGOV directly tracks the Federal Funds rate. In the current environment (early 2026), with the Fed Funds rate still relatively elevated by historical standards, SGOV yields in the 4–5% range — better than many high-yield savings accounts, with the added safety of direct Treasury ownership.

Tax note: Interest from U.S. Treasury bills is exempt from state and local income taxes (though not federal). For investors in high-tax states like California or New York, this is a meaningful advantage over corporate bond funds or money market accounts that don't offer this exemption.

Who SGOV is for:

• Investors who want a safe place to park cash that's not a savings account
• People holding cash waiting to invest (buying opportunity reserve)
• Conservative investors or retirees who want yield without duration risk
• Anyone who doesn't want to lock up money in CDs or longer-duration bonds

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Short Duration vs. Long Duration: Why It Matters

This is the central concept in bond investing.

Short-duration bonds (like SGOV):

• Mature quickly, so you get your money back and can reinvest at new rates
• Price barely moves when interest rates change
• Currently offering competitive yields

Long-duration bonds (like BND/AGG):

• Take years to mature — you're locked into the coupon for longer
• Prices move significantly when rates change
• Offer potentially higher yield as compensation for the extra risk
• Provide more portfolio ballast in a stock market crash (stocks and bonds often move inversely)

In a period of rising rates (like 2022), short-duration wins. In a period of falling rates, long-duration wins as prices appreciate. Nobody knows consistently which environment we'll be in.

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The Role of Bonds in a Portfolio

The traditional argument for holding bonds alongside stocks is correlation reduction. Historically, when stocks fall sharply (financial crisis, COVID crash), investors flood into Treasuries, which drives bond prices up. A 60% stock / 40% bond portfolio typically experiences much smaller drawdowns than a 100% stock portfolio.

The 2022 experience complicated this narrative: both stocks and bonds fell simultaneously as inflation forced rapid rate hikes. It was a reminder that bond funds are not risk-free, and that the stock/bond diversification benefit is stronger in deflationary or disinflationary environments than inflationary ones.

That doesn't mean bonds are useless — it means understanding which bonds you own and why matters.

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A Simple Framework

• If you want core fixed-income diversification: BND or AGG — pick one, low cost, broad exposure
• If you want to park cash with yield and no rate risk: SGOV (or USFR, another Treasury bill ETF worth knowing)
• If you want somewhere between: Consider BSV (Vanguard Short-Term Bond ETF) or SHY (1-3 year Treasury ETF) — shorter duration than BND but longer than SGOV

For most investors under 40 with long time horizons, the allocation to bonds should be small (0–20% of a portfolio). As you approach retirement, shifting toward bonds reduces sequence-of-returns risk — the danger that a market crash right before or early in retirement decimates your portfolio permanently.

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Screen for Income Opportunities

Beyond bond ETFs, dividend stocks offer another source of regular income — sometimes with better after-tax treatment than bond interest. The Value of Stock Screener lets you filter high-yield stocks by payout sustainability, earnings quality, and valuation.

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Further Reading

The Bond Book by Annette Thau is the most comprehensive plain-English guide to fixed-income investing available. If you want to understand bond math, duration, credit risk, and how different bond types behave across interest rate cycles, this is the book to read.

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This article is for informational and educational purposes only. Nothing here is financial advice. Always do your own research before making investment decisions.