Two funds track the same index. One charges 0.05% and quotes a 0.20% spread; the other charges 0.25% and quotes 0.02%. Which is cheaper depends entirely on how long you hold it.
An exchange-traded fund (ETF) lives in two markets at once. The secondary market is the exchange, where end investors buy and sell existing shares from each other or from a market maker through a brokerage account, intraday, at market prices. The issuer is not a party to those trades and receives no cash from them. The primary market is an over-the-counter (OTC) channel between the issuer and a small set of large broker/dealers called authorized participants (APs). Primary market activity is the only way ETF share count changes.
Each business day the issuer publishes a creation basket, the list of securities and cash an AP must deliver to receive new shares. That same basket sets the fund's intraday fair value. Trades occur in blocks called creation units, commonly 50,000 shares but ranging roughly from 10,000 to 600,000.
Common mistakes
- Treating a premium as free money for the investor. A premium paid on entry is a real cost; it is only an opportunity for an AP who can execute both legs, and only above the arbitrage band (0.08% in Example 2).
- Ranking funds on expense ratio alone. ETF B's 0.25% fee looks worse until the horizon is three months, where its total cost of $8,250 beats $21,250.
- Reading tracking error as underperformance. A 0.012% tracking error says nothing about direction. The median tracking difference, for example 0.79% against a 0.69% fee, carries the shortfall.
Bottom line
- Primary market: authorized participants only, in-kind creation/redemption in creation units, commonly 50,000 shares, range 10,000 to 600,000
- Secondary market: all end investors, exchange traded intraday, T+2 settlement in the US, six days for market makers, fragmented OTC across 29 depositories in Europe
- Tracking sources: fees, sampling/optimization, depositary receipts and ETFs, index changes, accounting practices, regulatory and tax rules, manager operations such as securities lending
- Tracking error is the standard deviation of daily differences; tracking difference over holding periods carries the direction and size
Exam shortcut
Read the horizon before you read the fees. "Three-week tactical tilt" means spread wins; "core holding" means expense ratio and tracking difference win. Set one-time cost plus annual cost times t equal across two funds and solve for t; the answer choices usually bracket the break-even.
The full lesson (about 2,783 words, 19 min read) adds 2 worked examples, all 5 common mistakes, a self-check, free in the app.
Learning objectives
- etf mechanics
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