How ETF Bid-Ask Spreads Affect Small Investors

For small accounts, the bid-ask spread on an ETF—the gap between the price you pay and what you can immediately sell for—can cost far more than the fund’s annual expense ratio. An investor buying $2,000 in a wide-spread ETF might lose $20 to the spread alone, dwarfing the $2–4 in annual fees. Choosing liquid ETFs is not optional.

How the spread works

When you buy an ETF, you pay the ask price—the price at which market makers and sellers are willing to transact. When you sell, you receive the bid price—the price at which buyers are willing to transact. The difference is the spread.

On the S&P 500 ETF (SPY), the bid-ask spread is typically $0.01 per share. If SPY is quoted at 450.00 bid / 450.01 ask, you pay 450.01 to buy and receive 450.00 to sell. Round-trip, you’ve surrendered 0.01 / 450 = 0.0022%, or roughly $0.22 on every $10,000 invested. Negligible.

On a less liquid ETF—say, a micro-cap value fund or an emerging-market bond strategy—the spread might widen to $0.50 or $1.00 per share. If the ETF trades at 50.00 bid / 51.00 ask, you’ve lost $1 immediately. On a $5,000 position, that’s a 0.2% hit just from entry. Selling later incurs another spread, bringing the total to 0.4%.

The spread reflects market-maker risk. When you buy from a market maker, she is now long the ETF and exposed to price moves before she can sell it to someone else. Wide spreads indicate that liquidity is thin—few other buyers want the ETF at the moment—so the market maker demands compensation for the risk of holding it. Liquid ETFs (large, popular, underlying holdings are themselves liquid) have tight spreads because the market maker can rehedge quickly. Illiquid ETFs have wide spreads because rehiring is slow and risky.

The math for small accounts

Spreads are a flat-dollar cost; expense ratios are a percentage. For large accounts, percentages dominate. For small accounts, the flat cost dominates.

Example 1: Buying $10,000 of SPY (S&P 500 ETF)

• Bid-ask spread: 0.01%
• Cost: $1
• Expense ratio: 0.03% annually
• Annual fee: $3
• In year 1, the spread ($1) is small relative to the fee ($3). But the spread is paid once; the fee recurs.

Example 2: Buying $2,000 of an illiquid small-cap value ETF

• Bid-ask spread: 0.8%
• Cost: $16
• Expense ratio: 0.25% annually
• Annual fee: $5
• The spread ($16) is more than three times the annual fee. If you hold for 2 years, the spread cost exceeds all management fees combined.

Example 3: Buying $500 of an emerging-market bond ETF

• Bid-ask spread: 1.2%
• Cost: $6
• Expense ratio: 0.35% annually
• Annual fee: $1.75
• The spread ($6) is more than three times the annual fee.

For accounts under $5,000, spread costs can exceed expense ratios indefinitely. The math is unforgiving: you are paying a one-time percentage tax at entry, then an annual percentage tax on top of it.

Identifying liquid vs. illiquid ETFs

Liquidity varies by ETF family, size, and category:

Highly liquid ETFs (spreads: 0.01–0.05%)

• Index Fund tracking the S&P 500: SPY, IVV, VOO
• Broad market index trackers: VTI, SWTSX
• Bond ETF tracking major indices: BND, AGG, LQD
• Popular Sector Rotation funds: XLK, XLV, XLY
• These are the industry workhorses. Trillions in assets; millions of shares trade daily.

Moderately liquid ETFs (spreads: 0.1–0.5%)

• Factor Investing ETFs: VTV (value), VUG (growth), QUAL (quality)
• International Equity ETF trackers: VEA, VXUS
• Industry-specific or subsector funds with billions in assets
• Still very tradeable; spreads are manageable for accounts over $5,000.

Illiquid ETFs (spreads: 0.5–2%+)

• Thematic ETF focused on niche trends (space stocks, clean energy, biotech)
• Narrow-country or narrow-sector funds (single-country emerging markets, biotech)
• New or small ETFs with less than $100M in assets
• International bond ETFs with foreign withholding complexity
• These are traps for small accounts. Avoid unless you have strong conviction and size.

A quick check: look up the ETF on your broker’s website and see the real-time bid-ask spread. Do not assume. Advertised spreads are averages; they widen during market stress or illiquid hours.

Strategies for small investors

1. Stick to megacap index funds. SPY, VOO, VTI, and their equivalents are the cheapest entry points. Expense ratios are 0.03–0.04% annually. Spreads are nearly zero. For a small account building a baseline portfolio, there is no excuse to go elsewhere.

2. Check the spread before buying. On your broker platform, place a mock order and observe the bid-ask. If the spread is more than 0.1%, reconsider. If it’s more than 0.5% and your account is under $10,000, skip it entirely.

3. Use limit orders. Market orders (buy at the market price) guarantee execution but lock in the ask. Limit orders (buy only at a specified price or better) let you try to split the spread. Set a limit order halfway between bid and ask. You might not fill immediately, but if you’re patient, you’ll save money.

Example: An ETF is quoted 50.00 bid / 50.50 ask. Place a limit order to buy at 50.25. Wait. If the spread tightens or demand picks up, you fill and pocket the 0.25 improvement.

4. Build positions over time; don’t try to time. If you’re investing $2,000 a month into a small-cap ETF with a 1% spread, you’ll pay $20 per purchase. Instead, buy a mega-liquid broad-market index fund ($0.50 cost) and add a small position in the small-cap fund once or twice a year. The cost per trade is lower overall.

5. Avoid ETFs with suspiciously high expense ratios and low assets. Expense ratios above 0.5% for equity funds and 0.3% for bond funds often reflect low asset bases. High expense ratios + low assets = wide spreads. The fund issuer can’t make the math work and will eventually close it. You don’t want to hold it.

The illusion of “cheap” funds

Some investors are seduced by expense ratios. A fund charging 0.08% feels cheaper than one charging 0.15%. But if the 0.08% fund has a 1.5% spread and the 0.15% fund has a 0.02% spread, the cheaper fund is a trap. Over 10 years, the spread cost dominates by an order of magnitude.

Always ask: What is the total cost of entry? This includes the bid-ask spread, any trading commissions (usually zero on modern brokers), and the fund’s expense ratio. For small accounts, the spread is the decisive factor.

Liquidity and market stress

Spreads widen dramatically during market volatility. A normally tight spread can blow out to 0.5% or more during a crash or a sector panic. If you need to exit quickly during a crisis, you’ll pay dearly.

This is another reason to favor liquid mega-cap funds: even in stress, SPY’s spread remains under 0.05%. Illiquid thematic ETFs can spike to 2–3% during selloffs, locking in devastating losses for exits.

See also