Everybody picks a whole number from 0 to 100. The winner is whoever comes closest to two-thirds of the average. Play it twice and watch the target retreat.
Paste straight from a form's response sheet or a spreadsheet: one person per line, the number last (for example Amara K, 33 or a copied row with a timestamp). Lines with no number between 0 and 100 are skipped and counted below the box. Everything stays in this browser.
Each step assumes everybody else reasoned one step less, and multiplies by two-thirds.
Almost nobody plays 0, and anybody who does loses. The winning number is a fact about the room, not about the game. In a second round everybody knows roughly what the room did, aims lower, and so lowers the target: the equilibrium is where the crowd is heading, not where it is.
Alain Ledoux used the game as a tie-break for 4,078 readers of his French puzzle magazine, asking for a positive whole number below a billion.
| Average | 134,822,738.26 |
| Target (two-thirds) | 89,881,825.51 |
| Winning guess | 89,793,238 |
| Missed by | 88,588 (0.009%) |
| Reasoning in the average | 3.2 steps from 500 million |
Keynes described the idea in 1936 as a newspaper beauty contest; Rosemarie Nagel's 1995 laboratory games found first-round averages around 36.