ETFs and funds
A fund is not an asset, it is a wrapper around assets plus a rule plus a fee, and an arbitrage loop between the fund and its underlying holdings is what keeps its price glued to what it actually owns.
A fund is not an asset; it is a wrapper around assets, plus a rule for what it holds, plus a fee. Analyzing one means analyzing all three, and the wrapper's plumbing matters more than most investors ever learn, right up until the day it matters enormously.
The machine: creation and redemption
An ETF stays glued to the value of its holdings through an arbitrage loop. Authorized participants (large market makers) can hand the issuer a basket of the underlying securities and receive new ETF shares, or hand back shares and receive the basket. If the ETF trades above its NAV, they create shares and sell them; below, they buy shares and redeem. The gap closes because someone profits by closing it.
ETF price > NAV -> APs create new shares, sell them -> price falls to NAV ETF price < NAV -> APs buy shares, redeem for basket -> price rises to NAV the loop is only as good as the underlying's liquidity: an ETF of illiquid bonds can trade at a real discount in stress, and in March 2020 several did, by design rather than malfunction: the ETF was the truer price.
The professional checklist, in order
- The index rule. An index fund tracks a rulebook, and the rulebook is the strategy: what qualifies, how it weights, when it rebalances. The S&P 500 is a committee-managed, float-weighted rule; a "high dividend" ETF is whatever its methodology document says. Read the methodology, not the name.
- Total cost, not just the fee. Expense ratio PLUS tracking difference (what the fund actually lagged its index, which nets fees, sampling, and securities-lending income back) PLUS the bid-ask spread you pay to trade it. A cheap fund with wide spreads is not cheap for anyone who transacts.
- Liquidity of the holdings, not the ETF. The ETF's own volume can be added to by the creation machine; the underlying market cannot. The stress behavior of a fund is its least liquid holdings' behavior.
- Structure details. Physical or synthetic replication, securities-lending policy, and for anything using futures (commodity ETFs) the roll rule, which decides how much contango bleed the holder eats.
- Concentration. Index weighting can quietly turn "diversified" into a bet: a cap-weighted tech index is a position in its top five names wearing a basket costume.
A 2x ETF delivers twice the DAILY return, and compounding daily resets means a volatile flat market grinds it down: up 10% then down 9.1% is flat for the index and negative for the 2x. These are trading tools with a holding period measured in days; held for months, the decay is not a flaw in the product, it is the product.
Judging active funds
The evidence is brutal and consistent: most active managers lag their benchmark after fees over a decade, and past outperformance barely predicts future outperformance. The professional questions for the exceptions: is the edge structural (process, mandate flexibility, genuine specialization) or was it one regime's style tailwind? Is active share high enough that the fee buys actual difference from the index, rather than an index fund with an active price tag? And is the fund's size still compatible with its strategy, since capacity is where good records go to die?
Flows: the wrapper as a market force
Funds are not passive observers of prices; their mechanics move prices. Index inclusion forces every tracker to buy on a known date. Cap-weighted flows buy more of what has risen, a structural momentum bid. Rebalance dates create predictable pressure that professionals trade around. And sector fund flows are a live sentiment gauge: money chases performance with a lag, so extreme inflows into a theme often mark its late innings. Reading flow data (weekly fund flows, ETF creations) is reading where the marginal, least-informed dollar is going.
| Wrapper | Best at | Watch |
|---|---|---|
| Broad index ETF | Cheap, tax-efficient market exposure | Concentration inside the index |
| Sector / theme ETF | Expressing a view without single-stock risk | Methodology drift; buying the theme's top |
| Bond ETF | Liquidity a bond portfolio lacks | Discounts in stress; duration of the rule |
| Commodity ETF | Access without a futures account | The roll rule IS the return |
| Active mutual fund / ETF | Genuine specialist mandates | Fee vs active share; capacity |
| Closed-end fund | Discount arbitrage; illiquid assets | Leverage and permanent discounts |
- NAV
- Valuing a company by pricing its assets directly and subtracting debt: properties at market cap rates for a REIT, reserves at forward prices for oil and mining. The gap between a stock and its NAV is those sectors' core debate.
- Authorized participant
- The large market makers allowed to create and redeem ETF shares against baskets of the underlying. Their arbitrage is the machine that keeps an ETF's price at its NAV.
- Creation / redemption
- The ETF mechanism: hand in the basket, receive shares, or the reverse. It is why ETF liquidity is really the underlying market's liquidity wearing a ticker.
- Expense ratio
- The fund's annual fee as a share of assets. The visible cost; tracking difference and trading spreads are the rest of the bill.
- Tracking difference
- What a fund actually lagged (or beat) its index over a period, netting fees, replication choices and securities-lending income. The honest cost number, and often smaller OR larger than the expense ratio.
- Index methodology
- The rulebook an index fund tracks: what qualifies, how it weights, when it rebalances. The rulebook IS the strategy; the fund's name is marketing.
- Active share
- How different a fund's holdings are from its benchmark. A low-active-share fund charging active fees is an index fund with a markup; the fee should buy difference.
- Fund flows
- Money moving into and out of funds, published weekly. Flows chase performance with a lag, so extreme inflows into a theme often date its late innings; index inclusion flows are forced buying on a schedule.
- Leveraged ETF decay
- Daily-reset leverage compounds against holders in volatile flat markets: up 10% then down 9.1% is flat for the index and negative for the 2x. These are day-count instruments; held long, the decay is the product.
- Closed-end fund
- A fund with a fixed share count that trades at whatever the market pays, routinely above or below its NAV. The discounts are a hunting ground and sometimes a value trap with leverage attached.
- Securities lending
- Funds lending their holdings to short sellers for a fee, which offsets costs (and explains some funds beating their own expense ratio). The revenue split and collateral policy are in the fine print.