You Think You're Smart With Money. You're Not.
A Nobel Prize-winning idea that explains why lottery winners go bankrupt, why your bonus disappears, and why your "emergency fund" is a financial trap.
Do you remember Sushil Kumar from Kaun Banega Crorepati, the one who actually won ₹5 crores? He came from very little before he won. He returned to nothing after. Five crores came and went, and he had nothing to show for it. How does that even happen?
The answer is embarrassingly simple. It comes down to how we mentally categorise money, and how badly that categorisation messes with our decisions.
What is Mental Accounting?
Richard Thaler, the same economist who later won the Nobel Prize, first wrote about this in a paper titled “Mental Accounting Matters.“ His observation was straightforward: people assign money different values depending on where it came from, and that quietly drives some of our worst financial decisions.
The technical term for what we should do is treat money as fungible, meaning ₹100 is ₹100, regardless of whether it came from your salary, a bonus, or a scratch card. We create little mental buckets instead, and the rules we apply to each bucket are completely different.
If you get a ₹1,00,000 year-end bonus, you are probably already spending it in your head: a trip, a new phone, dinner at that place you have been meaning to try. But if someone asked you to cut ₹1,00,000 from your monthly expenses, you would treat that as a crisis. It is the same amount. The math is indifferent to its origin. Your brain is anything but.
Why This Matters for Investing
Mental accounting gets especially dangerous when money is involved in markets.
Consider how people behave with capital gains. If you invest ₹10,000 of your salary and it grows to ₹20,000, most people become noticeably more reckless with the extra ₹10,000. They take risks they would never take with money they “actually earned.” Losing it would hurt just as much. Because it came from the market, it feels like house money.
The same logic plays out with lump sums versus monthly income. People who receive a large amount at once tend to park it in safe, low-yield options: fixed deposits, savings accounts. The same person, receiving that identical amount in smaller monthly instalments, would confidently put it into equities. The money is the same. The behaviour is worlds apart.
This is where the pyramid problem shows up in personal finance. When people mentally silo their money, one bucket for emergencies, one for retirement, one for fun, they stop seeing their finances as a whole. Someone might hold excessive cash in a savings account earning 3% while carrying credit card debt at 36%. On paper, that is indefensible. Mentally, those are two separate accounts with two separate sets of rules.
The Upside
Mental accounting, in fairness, has its uses. Earmarking money for specific goals, retirement, a child’s education, a home, genuinely helps people follow through. Someone who deposits a fixed amount into a retirement account every month is far more likely to retire with savings than someone who invests whatever is left over. The mental commitment creates real behavioural guardrails.
The system works. It just stops working the moment it starts overriding logic.
Where It Goes Wrong
Tax refunds are a good example. Most people treat a refund like a gift from the government. It is simply your own money that was withheld in excess. The government held it for a year, interest-free. You are getting back what was already yours. Because it arrives as a lump sum, it gets spent like a windfall rather than folded into a sensible financial plan.
Bonuses follow the same pattern. Lottery wins are the extreme case, and Sushil Kumar is the cautionary tale. The money feels different, so it gets treated differently, and “differently” almost always means worse.
Thaler’s larger point is worth sitting with. Conventional economics assumed people were rational. His entire career was built on demonstrating that they are predictably irrational, that the deviations follow patterns, and that those patterns can be studied and anticipated. We behave like humans who have invented their own rules about which money counts.
The Fix
Awareness is most of the work. Before spending a bonus, a refund, or any windfall, ask yourself whether you would spend regular income this way. If the answer is no, that is mental accounting at the wheel.
Treat all money as if it came from your salary. Run it through the same filters. Give it the same scrutiny. ₹100 is ₹100. It always was.