Bill comes back from August with a tan and a bank account that looks different from how he left it. He spent three weeks between a beach house with friends, a couple of concerts, and the kind of evenings that seem cheap in the moment because the bill gets split.
He sits down on the first Sunday of September and tries to reconstruct what happened.
He remembers the big items: his share of the beach house, the train tickets, the concerts. What he cannot account for is the rest. There is a gap between what he remembers spending and what the bank statement shows. The gap is not small.
Consumption bias is the systematic tendency to underestimate spending in categories that feel social or experiential. The cost of an evening out is not the dinner. It is the dinner plus the drinks after, plus the taxi, plus the round of shots someone suggested at midnight that felt free because no one was keeping score. Each individual item seems minor. The total is not.
Bill adds up everything the bank recorded during August. Then he adds up what he thought he spent. The difference between the two numbers is the bias made visible.
He has been back at work for a week and he already needs the next salary to feel comfortable again.
The tip
Before estimating what a social event will cost, add 40 percent. The gap between the planned number and the actual one is not a failure of willpower. It is a structural feature of how experiential spending works.
Consumption bias, August 2024: estimated spending 400, actual spending 680. Variance: -280. Cash position end of August: 1,410.
Bill is 24. He has just started his first job. Every episode, we read his personal ledger through accounting eyes. / FY 2024 ledger