Mental Accounting
The behavioral tendency to treat money differently based on its source or intended use, leading to irrational financial decisions.
What is Mental Accounting?
Mental accounting, a concept developed by economist Richard Thaler, describes how people categorize money into separate mental 'buckets' — salary, bonus, inheritance, casino winnings — and apply different spending and risk rules to each, even though all dollars are fungible. Investors might take aggressive risks with 'house money' (recent investment gains) while being ultra-conservative with their 'core savings,' despite the economic irrationality of this distinction. Mental accounting leads to suboptimal portfolio construction, irrational spending patterns, and failure to optimize taxes across accounts.
Example
A person receives a $5,000 tax refund and treats it as 'found money,' spending it on a vacation they would never have funded from regular income — even though the refund represents their own overpaid taxes. Similarly, investors often hold a losing stock in one mental account and a winning stock in another rather than evaluating the overall portfolio holistically.