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Investment Foundations

Mission 13 · Lesson 13.1 — Write the Rules and Defend the Portfolio

Aswath Damodaran, Investment Philosophies (Sessions 1, 6, 36 and 38 of 38); CFA Institute; SEC / Investor.gov

How this lesson uses themShow

Source-authentic claims follow Damodaran Sessions 1 (the investment process and why a philosophy is what you return to when strategies stop working), 6 (trading costs and how to manage taxes), 36 (why active managers fail, and that activity generates negative returns) and 38 (the self-assessment, the sleep, life-change and second-guessing tests, and the rule against mixing strategies with contradictory assumptions). All four carry official caption tracks. The IPS skeleton is CFA Institute's Elements of an Investment Policy Statement for Individual Investors, May 2010, cited for structure only — it specifies elements, not rates, so its age does not date it; its governance section assumes an institution and OPS states the adaptation for a solo investor on the page rather than dropping it silently. Rebalancing method and trigger types are the SEC's Beginners' Guide to Asset Allocation, Diversification, and Rebalancing, which gives two trigger types and explicitly leaves the number to the investor; any cadence or band the learner chooses is personal policy and is labelled as such. Order mechanics are the SEC's order-types guidance, including that a stop order becomes a market order once the stop price is reached. Four defects are recorded and handled rather than repeated: Session 36's performance percentages are dated and inherit Mission 10's quarantine, appearing as labelled history or not at all; Session 6's premise that dividends are taxed at a higher rate than capital gains is source-era and is not reproduced, since under current US rules the distinction turns on qualification and holding period; Vanguard's rebalancing research studies target-date funds, frames its benefit as higher returns and omits tax from its cost model, so it is not cited for the rebalancing rule at all; and the cached IRS publications extract with interleaved columns that splice unrelated sentences, so nothing is quoted from them — Publications 550, 590-A and 590-B (2025 editions) are cited by edition as the pointer of record. Tax appears only as directional warnings. Nothing here calculates personal tax liability, recommends account placement, rules on eligibility, ranks or scores a product, or authorizes a trade. Current portfolio weights in the rebalancing control room are an illustration: OPS stores targets and bands, not balances. The 80/100 transfer threshold is an OPS pilot design choice and is not represented as validated. Full audit: docs/source-audits/mission-13-capstone.md.

Mission 13Investment Foundations · Write the rules and defend the portfolio

Write the Rules and Defend the Portfolio

Twelve missions decided what you hold. This one decides what you do when the market falls, your income stops, or the reason you bought something turns out to be wrong — and whether the whole thing still fits the person who wrote it.

Your mission

Work one crash end to end, compare the three ways back to your target weights, write the rules you will have to obey when obeying them feels wrong, compile twelve missions into one document — then find what is wrong with a stranger’s portfolio.

Check readiness ↓

40 minutesEleven guided stagesOne saved set of operating rulesNeither state is advice

Guided operating lab

0 of 11 stages complete

OPS Guide

This is the only mission that cannot stand alone. It operates the portfolio the others built, so it needs their decisions — and it will tell you exactly which ones are missing rather than failing quietly.

Read what is ready and what is not, then continue.

Stage 1 of 11 · Readiness

What this mission needs from the other twelve

12 of 12 checkpoints need attention

You can work through this mission either way. What changes is the state you finish in: a practice plan needs nothing from the list, a plan you could actually operate needs all of it.

Checkpoint readiness
Checkpoint	State	Why this mission needs it
Goal and limits — what the money is for, by when, and the loss you can take	empty	Every scenario is judged against the goal you wrote.
Market beliefs — the view the whole plan rests on	empty	—
Bond risk policy	empty	—
Required return	empty	—
Strategic allocation — the weights and their bands	empty	The control room cannot measure drift without your weights.
Business evidence	empty	—
Valuation gate	empty	—
Friction budget — what any action costs you	empty	Rebalancing cost is charged from this budget.
Evidence test — the bar a claim must clear	empty	—
Architecture licence — passive core and benchmark	empty	The benchmark your result is measured against comes from here.
Timing policy — whether deviation is allowed at all	empty	A rebalance is not a tactical deviation, and this says which is which.
Holdings list — exact products, costs and source dates	empty	Your plan records product identity and source dates from here.