ETF Bid-Ask Spread

An ETF bid-ask spread is the difference between the highest price at which someone will buy an ETF (the “bid”) and the lowest price at which someone will sell it (the “ask”). For a large, liquid equity ETF, the spread is typically 0.01%–0.05%, meaning that on a $100 position, you might lose $0.01–0.05 to the spread. Spreads widen during market stress and for less liquid ETFs.

How bid-ask spreads work

At any moment, an ETF has a “bid” price and an “ask” price:

• Bid: The highest price anyone is currently willing to pay. If you want to sell, you get the bid price.
• Ask: The lowest price anyone is currently willing to accept. If you want to buy, you pay the ask price.

Suppose SPY (S&P 500 ETF) is trading:

Bid: $415.00
Ask: $415.01
Spread: $0.01 (or 0.0024%)

If you buy 100 shares, you pay $415.01 × 100 = $41,501. If you immediately sell those same 100 shares, you receive $415.00 × 100 = $41,500. You lost $1 to the spread.

Why spreads exist

ETF spreads are quoted by market makers and authorized participants, who profit from them. The spread compensates them for:

1. Inventory risk. If a market maker buys 10,000 ETF shares to facilitate a sell order, they hold inventory that could move against them. The spread is compensation for that risk.

2. Operational costs. Quoting, monitoring, and executing trades costs money.

3. Adverse selection risk. If someone is hitting the bid or lifting the ask aggressively, the market maker worries they have bad information and may be about to lose money. Wider spreads protect against this.

Spreads across different ETFs

Large, liquid ETFs have tight spreads because:

• High trading volume. Many buyers and sellers mean market makers turn inventory quickly.
• Authorized participants. Multiple APs actively create and redeem shares, providing a constant supply of inventory.
• Tight premium/discount. The threat of arbitrage keeps prices in line, reducing inventory risk.

Small, specialized ETFs have wider spreads because:

• Low volume. Few daily trades mean market makers must hold inventory longer.
• Illiquid holdings. If the ETF holds illiquid bonds or emerging market stocks, the cost for a market maker to hedge inventory is high.
• Limited APs. If only one or two APs actively service the fund, they have less competition and can quote wider spreads.

Typical spreads:

• SPY (S&P 500): 0.01% (extremely liquid)
• VTI (total US market): 0.02%
• BND (broad bond): 0.03%
• Small niche ETF: 0.1%–0.5%
• Very illiquid ETF: 1.0%+

How spreads impact costs

On a single trade, a tight spread of 0.02% on a $10,000 investment costs $2. That seems trivial. But consider a long-term investor:

• Buy: $10,000 investment, lose 0.02% to spread = $2 loss
• Sell 30 years later: $100,000 portfolio (assuming 10% annual returns), lose 0.02% to spread = $20 loss
• Total cost from spreads: $22 (plus the opportunity cost of that $2 compounded for 30 years)

For a trader making 100 round-trip trades per year, the spread cost becomes material.

Spreads during market stress

During market turmoil, spreads widen dramatically:

March 2020. During the COVID market crash, spreads on bond ETFs and emerging market ETFs widened from 0.05% to 0.50% or more, as market makers pulled back due to reduced capital and increased risk.

Flash crashes. During brief, violent market moves, spreads can widen to 1%+ as algorithms and market makers shut down.

Retail investors discovered this in March 2020 when trying to buy bond ETFs at what they thought were bargain prices, only to find bid-ask spreads had widened so much that they were overpaying.

Monitoring spreads

Most broker platforms display bid-ask spreads in real time. You can see them on:

• Your broker’s trading platform
• Financial websites (Yahoo Finance, Google Finance, TD Ameritrade)
• Specialized tools (FINRA’s Market Data Center, SEC data)

Before trading a specialized or less liquid ETF, check the current bid-ask spread. A sudden widening can be a signal that the ETF is facing liquidity issues.

Spreads versus expense ratios

Do not confuse bid-ask spreads with expense ratios:

• Bid-ask spread: Paid once when you buy or sell. A cost of trading.
• Expense ratio: Charged annually. A cost of holding.

An ETF with a tight spread (0.02%) but a high expense ratio (0.50%) is still expensive if you hold it long-term.

See also