The Pyramid Friendship Clubs had members recruit two other members, charge them a fee and pass part of that fee to the person who had recruited them who then passed part up to the next person and so on. This results in exponential growth which stops when the scheme runs out of suckers.
| 1000 AD | Persians or Indians? | Grains of wheat on a chessboard |
| 1973 AD | Black, Scholes & Merton | Black-Scholes |
| 1949 AD | Californians | Pyramid schemes |