Mental accounting.
In plain English
Mental accounting is the habit of sorting money into separate mental buckets by source or purpose and treating those buckets differently, even though money is fungible and a dollar spends the same wherever it sits. Thaler described it in 1999 as the cognitive operations people use to track their finances. It can help, like keeping a bucket you refuse to touch for retirement, or hurt, like splurging a tax refund you would never spend from your paycheck, or carrying credit-card debt at high interest while guarding a low-yield savings bucket.
01Why it matters
Because a dollar is worth the same regardless of its bucket, mental accounting can lead to choices like paying card interest while sitting on savings, so seeing the buckets helps you decide with the whole picture.
02The math, step by step
Someone treats a tax refund as fun money and blows it, though they would never spend the same amount from their salary, and meanwhile keeps 2,000 dollars in savings earning little while carrying a card balance at high interest. Same dollars, different mental buckets, costlier result.
03What this is NOT
It is not the same as a deliberate budget. Assigning money to goals on purpose is a useful tool. Mental accounting is the automatic, sometimes costly, tendency to treat identical dollars differently based on their bucket, even against your own interest.
04Receipts
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