the laws library
100 famous laws of business & psychology
The named laws, principles, and effects that explain how customers choose, how teams behave, how markets move, and why plans go wrong. Each one comes with where it came from, real business examples, steps to apply it, and the most common way people misread it.
Business & strategy laws
The rules of thumb that keep showing up in companies of every size: where results really come from, why plans fail, and how incentives and systems behave once real people get involved.
Pareto Principle (80/20 Rule)
Roughly 80% of results come from 20% of causes — a small share of customers, products, or efforts drives most of the outcome.
Murphy's Law
Anything that can go wrong will go wrong — so design plans, processes, and products assuming failure will eventually happen.
Goodhart's Law
When a measure becomes a target, it stops being a good measure — people optimise the number instead of the result it was meant to track.
Gall's Law
A complex system that works is always found to have evolved from a simple system that worked — complex systems designed from scratch rarely do.
Sturgeon's Law
Ninety percent of everything is crud — in any field, most output is mediocre, so quality is judged by the best ten percent.
Lindy Effect
For non-perishable things like ideas, books, and technologies, every extra year of survival implies a longer remaining life expectancy.
Matthew Effect
Advantage compounds: those who already have status, customers, or capital tend to gain more, while those behind fall further back.
Law of Unintended Consequences
Actions taken by people, companies, or governments always have effects that were not intended — some helpful, some harmful.
Cobra Effect
An incentive meant to solve a problem makes it worse because people find a way to profit from the problem itself.
Chesterton's Fence
Don't remove a rule, process, or ‘fence’ until you know why it was put there in the first place.
Occam's Razor
When several explanations fit the facts, prefer the simplest one — the one that needs the fewest assumptions.
Hanlon's Razor
Never attribute to malice what is adequately explained by mistake, ignorance, or busyness.
Law of the Instrument (Maslow's Hammer)
People over-rely on the tool or skill they know best — if all you have is a hammer, every problem looks like a nail.
Amara's Law
We tend to overestimate the effect of a new technology in the short run and underestimate it in the long run.
Metcalfe's Law
The value of a network grows roughly with the square of its number of users — each new member adds value for everyone already there.
Moore's Law
The number of transistors on a chip doubles about every two years — shorthand for computing getting exponentially cheaper and more powerful.
Kidlin's Law
If you can write the problem down clearly, the matter is half solved.
Streisand Effect
Trying to hide, remove, or censor information usually makes it spread further.
Economics & market laws
The economic forces behind every price tag, cost curve, and competitor move — explained without the textbook graphs, and translated into decisions you can make this week.
Law of Supply and Demand
Prices rise when demand exceeds supply and fall when supply exceeds demand, settling where the two meet.
Law of Diminishing Marginal Utility
Each additional unit of something gives less extra satisfaction than the one before.
Law of Comparative Advantage
Everyone gains when each party specialises in what it gives up least to produce, and trades for the rest — even if one party is better at everything.
Gresham's Law
Bad money drives out good: when two forms of money have the same official value, people hoard the more valuable one and spend the other.
Jevons Paradox
Making a resource more efficient to use can increase total consumption of it, because it becomes cheaper and more useful.
Say's Law
Production creates the income that funds demand — summarised (and debated) as ‘supply creates its own demand’.
Engel's Law
As household income rises, the share spent on food falls — even though the absolute amount spent on food may rise.
Law of One Price
In an efficient market, identical goods should sell for the same price everywhere, after accounting for transport and taxes.
Veblen Effect (Veblen Goods)
For some luxury goods, demand rises as price rises, because a high price signals status.
Tragedy of the Commons
When a shared resource is open to everyone, individuals acting in their own interest tend to overuse and ruin it.
Wright's Law (Experience Curve)
Every time cumulative production doubles, the cost per unit falls by a roughly constant percentage.
Law of Diminishing Returns
Adding more of one input while others stay fixed eventually produces smaller and smaller increases in output.
Baumol's Cost Disease
Services with little productivity growth, like education and healthcare, get steadily pricier because their wages must keep pace with more productive sectors.
Hotelling's Law
Competitors tend to make their products very similar and cluster together, because each one moves toward the middle of the market.
Marketing, sales & UX laws
How customers notice, remember, and choose: positioning laws from classic marketing, plus the design laws that decide whether a page, a pack, or a store actually converts.
Law of Leadership (Marketing)
It is better to be first in the customer's mind than to be better — the first brand in a category usually stays the leader.
Law of the Category
If you can't be first in a category, create a new category you can be first in.
Law of Focus
The most powerful idea in marketing is to own a single word or idea in the customer's mind.
Rule of Seven (Marketing)
A prospect typically needs to see or hear a message several times — traditionally ‘seven’ — before taking action.
Banner Blindness
People learn to ignore anything that looks like an ad, so banner-style content is often not seen at all.
Jakob's Law
Users spend most of their time on other sites, so they expect yours to work the same way as the ones they already know.
Hick's Law
The time it takes to make a decision increases with the number and complexity of choices.
Fitts's Law
The time to reach a target depends on its distance and size — big, close targets are fastest to hit.
Miller's Law
People can hold only a few items in working memory at once — so chunk information into small groups.
Tesler's Law
Every system has a certain amount of complexity that cannot be removed — only moved between the user and the business.
Doherty Threshold
Productivity and engagement soar when a system responds in under about 400 milliseconds.
Aesthetic-Usability Effect
People perceive attractive designs as easier to use and are more forgiving of their flaws.
Von Restorff Effect
When several similar items are present, the one that differs from the rest is most likely to be remembered.
Serial Position Effect
People best remember the first and last items in a series, and tend to forget the middle.
Peak-End Rule
People judge an experience mostly by how it felt at its most intense moment and at its end, not by the average.
Gestalt Law of Proximity
Objects placed close together are seen as belonging to the same group.
Persuasion & consumer psychology
The psychological principles behind why people say yes — Cialdini's principles of influence and the behavioural-economics effects that shape every price, offer, and pitch. Use them honestly.
Law of Reciprocity
People feel obliged to return favours — when you give first, others are more likely to give back.
Scarcity Principle
People value things more when they are rare, limited, or about to run out.
Social Proof
When unsure, people look at what others like them are doing and copy it.
Authority Principle
People tend to follow and trust those who appear to be credible experts or authorities.
Liking Principle
People are more easily persuaded by those they like — people who are similar, friendly, and familiar.
Commitment and Consistency Principle
Once people commit to something, especially publicly or in writing, they feel pressure to act consistently with it.
Unity Principle
People are more influenced by those they see as part of their own group — a shared identity of ‘we’.
Anchoring Bias
The first number people see heavily influences their later judgements, even if that number is irrelevant.
Loss Aversion
Losses feel roughly twice as painful as equivalent gains feel good, so people work harder to avoid losing than to win.
Endowment Effect
People value things more simply because they own them.
IKEA Effect
People place higher value on things they have helped create, even partly.
Mere Exposure Effect
People tend to like things more the more often they are exposed to them.
Paradox of Choice
Too many options can overwhelm people, making them less likely to choose and less satisfied when they do.
Framing Effect
The same information leads to different decisions depending on how it is presented.
Weber–Fechner Law
People notice changes relative to the starting amount, not in absolute terms — a ₹50 change matters on ₹200 but not on ₹20,000.
Pratfall Effect
Competent people and brands become more likeable when they show a small mistake or flaw.
Zeigarnik Effect
People remember unfinished or interrupted tasks better than completed ones.
Ben Franklin Effect
People who do you a favour tend to like you more afterwards — asking for help can build a relationship.
Cognitive biases & decision-making
The predictable mental shortcuts that mislead owners, managers, and investors — and the simple habits that catch them before they turn into expensive decisions.
Dunning–Kruger Effect
People with low skill in an area tend to overestimate their ability, while experts often underestimate theirs.
Confirmation Bias
People search for, notice, and remember information that confirms what they already believe, and ignore what contradicts it.
Sunk Cost Fallacy
People keep investing in a failing project because of what they have already spent, rather than what it will cost from here.
Survivorship Bias
Drawing conclusions only from the winners who survived, while ignoring the many who failed, leads to false lessons.
Availability Heuristic
People judge how likely something is by how easily examples come to mind, not by actual frequency.
Halo Effect
One positive trait — like looks, fame, or a single success — makes people judge everything else about a person or brand more favourably.
Planning Fallacy
People underestimate how long tasks will take and how much they will cost, even when they know past projects ran over.
Hindsight Bias
After something happens, people believe they predicted it or that it was obvious all along.
Status Quo Bias
People prefer things to stay the same and tend to stick with defaults, even when change would benefit them.
Optimism Bias
People believe they are less likely than others to experience bad outcomes and more likely to experience good ones.
Spotlight Effect
People overestimate how much others notice their appearance, mistakes, and actions.
Baader–Meinhof Phenomenon
After you notice something for the first time, you start seeing it everywhere — and wrongly assume it has become more common.
Yerkes–Dodson Law
Performance improves with stress or arousal up to a point, then declines when pressure gets too high.
Hedonic Treadmill
People quickly adapt to improvements in their lives, so happiness tends to return to a baseline after gains or losses.
Thorndike's Law of Effect
Behaviours followed by satisfying results are more likely to be repeated; those followed by unpleasant results are less likely.
Curse of Knowledge
Once you know something, it is hard to imagine not knowing it — so experts explain things badly to beginners.
Productivity & time laws
Why work expands, why everything takes longer than planned, and why the important task keeps getting pushed to tomorrow — plus the fixes that actually stick.
Parkinson's Law
Work expands to fill the time available for its completion.
Hofstadter's Law
It always takes longer than you expect, even when you take into account Hofstadter's Law.
Carlson's Law
Work done in one continuous block takes less time and energy than the same work done in interrupted pieces.
Illich's Law
Beyond a certain number of hours, productivity falls and can turn negative — more work stops producing more results.
Laborit's Law
People naturally avoid unpleasant tasks and seek immediate rewards — so the hardest, most important work gets postponed.
Ninety-Ninety Rule
The first 90% of a project takes 90% of the time; the remaining 10% takes the other 90%.
Parkinson's Law of Triviality (Bikeshedding)
Groups spend disproportionate time on trivial issues and too little on complex, important ones.
Premack Principle
A preferred activity can be used to reward a less preferred one — do the hard thing first, then the enjoyable thing.
Leadership, teams & operations
What happens to people, teams, and processes as a business grows — promotions, team size, coordination, expectations, and the maths of getting work through the system.
Peter Principle
In a hierarchy, people tend to be promoted until they reach a role they are not competent at — and stay there.
Brooks's Law
Adding people to a late project makes it later.
Conway's Law
Organisations design systems and products that mirror their own communication structures.
Price's Law
In any group, roughly the square root of the number of people produce half of the output.
Dunbar's Number
People can maintain only around 150 stable social relationships at a time.
Ringelmann Effect
As group size increases, individual effort tends to decrease.
Pygmalion Effect
Higher expectations from leaders lead to higher performance from the people they lead.
Hawthorne Effect
People change their behaviour when they know they are being observed or studied.
Little's Law
Average work in progress equals throughput multiplied by average time each item spends in the system (L = λW).
Pournelle's Iron Law of Bureaucracy
In any bureaucracy, the people devoted to the organisation itself eventually gain control over those devoted to its goals.