Mutual Fund

A mutual fund pools money from thousands of investors and hands it to a professional manager who buys a portfolio of stocks, bonds or both. You own units of the pool, and your units' value rises and falls with the portfolio.

Unlike an ETF, a mutual fund does not trade on an exchange. You buy and sell directly with the fund itself, once per day, at the Net Asset Value (NAV) calculated after the market closes. Whatever time you place your order today, you get today's closing NAV.

Funds come in two broad kinds: index funds, which cheaply track a market, and active funds, which charge more to try to beat it. Decades of evidence show most active funds lag their index after fees — which is why costs are the single best predictor of fund performance.

The mechanics

• NAV = (assets − liabilities) / units outstanding, struck daily using closing prices.
• Forward pricing: orders received before the cut-off get today's (unknown) NAV — this kills intraday timing games.
• Flows: new money creates units; redemptions destroy them. The manager must invest inflows and raise cash for outflows, which creates transaction costs borne by everyone in the pool.

Fee anatomy

• Ongoing charge / expense ratio — management + admin, deducted daily inside NAV.
• Loads — entry/exit sales charges (increasingly rare).
• Performance fees — a share of returns above a hurdle, ideally with a high-water mark.

Share classes and wrappers

The same portfolio is often sold in multiple share classes (retail vs. institutional fees, distributing vs. accumulating, currency-hedged). In Europe the dominant legal wrapper is UCITS, with strict diversification and liquidity rules.

Performance measurement

Fund skill is estimated by regressing excess returns on factor benchmarks, e.g. the Carhart four-factor model:

Only \(\alpha\) is skill; the betas are cheap exposures an index fund could deliver. Reported \(\alpha\) must clear fees and survivorship bias — dead funds vanish from databases and flatter the average.

Compounding of costs

With gross return \(g\) and total cost \(c\), terminal wealth after \(T\) years scales as \(\big(\frac{1+g-c}{1+g}\big)^T\) of the costless outcome — the fee drag compounds geometrically, which is the quantitative core of the index-fund argument.

Liquidity transformation risk

Daily-dealing funds holding illiquid assets (credit, small caps, property) perform maturity transformation without a lender of last resort. Redemption runs force fire sales; remaining investors bear the cost. Tools: swing pricing (adjusting NAV by a factor \(\pm s\) when net flows exceed thresholds), gates, and in-kind redemption.

The formulas above are standard textbook formulations, simplified for teaching. They explain the mechanism — they are not a valuation tool, and they will not reproduce a dealer’s price.