Rules-Based Quantitative Investing
Replace emotional investment decisions with predefined buying and selling rules
- Difficulty
- Moderate
- Time to result
- ~weeks to results
- Steps
- 5
- Confidence
- 98%
This method turns investing into a repeatable decision process. Start with an investable universe, then establish simple rules that determine which assets qualify, when to buy, and when to sell. Test the same logic across multiple historical market environments to understand both its potential and its limitations. The mechanism is behavioral as much as mathematical: rules create a foundation of logic that prevents product enthusiasm, dislike of management, overconfidence, or recent performance from becoming the investment thesis. Faber presents this as his response to recognizing his own tendency to take too much risk. The process only remains useful when the selected style also fits the investor's psychology well enough to be followed consistently.
Origin
Meb Faber said painful trading losses and recognition of his own behavioral biases pushed him toward rules-based quantitative investing.
Core principles
- 01Logic should govern decisions instead of emotion
- 02Buying and selling rules must be specified in advance
- 03Historical testing reveals how a system behaved across environments
- 04A usable style must fit the investor's psychology
How to run it
- 1
Choose the universe
Define the stocks, markets, or asset classes to which the process will apply.
Pro tip Keep the universe broad enough to avoid depending on one company or regime.
- 2
Specify buying rules
Write objective conditions that determine which investments qualify and when they can be bought.
Watch out Do not substitute affection for a product or company for a rule.
- 3
Specify selling rules
Define the conditions that remove an investment before capital is committed.
Pro tip Make the exit as explicit as the entry.
- 4
Test across history
Examine how the same logic would have performed in different market environments and long-running regimes.
Pro tip Include environments unlike the one you personally experienced.
Watch out Historical testing shows what was possible, not what is certain.
- 5
Match the style to yourself
Assess whether the process controls your biases and is tolerable enough to follow through difficult periods.
Pro tip Prefer a process that lets you sleep and remain invested.
Watch out A sound method fails in practice if you abandon it under stress.
In the wild
Faber explains that a rules-based stock process prevents an investor from buying merely because they love Apple products or avoiding a company because they dislike its CEO. The stock must satisfy the same buying and selling logic as every other candidate.
→ The decision rests on consistent evidence rather than personal attachment.
After losing money and recognizing that he was overconfident and inclined to take too much risk, Faber made rules for himself rather than relying on discretion.
→ The rules constrain the behavioral tendencies most likely to damage his portfolio.
Common mistakes
Letting emotion override the rules
Product enthusiasm, dislike of a CEO, or fear turns a consistent process back into discretionary guessing.
Testing only one market regime
A process fitted to a recent environment may fail when conditions change for years or decades.
Is it for you?
Best for
Investors who recognize that their emotions and biases undermine discretionary decisions.
Not ideal for
Investors unwilling to follow a predefined process through periods when it underperforms.
From the transcript
“There's rules to sort investments, so say stocks, for example, to be able to say, look, we're gonna pick these stocks based on these rules…”
“I need to make rules for myself, otherwise I'll do the dumbest possible things you know out there”
“It allows you to look back in history on how such a system would have performed, how that logic would have done in various market…”
From the episode
Cambria CIO Meb Faber: Masters in Business (Audio)
Meb Faber