Instructions. Please read them carefully.

Welcome to our experiment! _ people, that is you and _ others, have joined us.

Your decision.
You will receive 20 coins per round for _ rounds. Each round, you will have to choose how many coins to put directly into your personal account, and how many coins to put into a group account.

Ordered group matching.
Each round you will be assigned to a new group of 4 people, that is, you and three (possibly different) others. Which group you are assigned to depends on your and others contributions to the group account.

All contributions will be ranked from highest to lowest. The first 4 people in the list form Group 1, the next 4 people in the list form Group 2, the third 4 people in the list form Group 3, and the last 4 people form Group 4.

In case two or more players contributed equally in the same round, their relative position in the ranking will be decided randomly.

Return from personal account.
Each coin that you put into your personal account each round goes one-to-one towards your final earnings in the game.

Return from group account.
Each coin that you put into the group account will pay you back some positive amount of money as described below.

The total amount of coins in your group account is equal to the sum of the contributions to the group account by each of the group members. That amount is then multiplied by 2 and distributed equally amongst group members. In other words, you will get a return equal to half of the group account total.

Total number of coins in your groupYour return
00
105
157.5
2814
......
8040
Any amountHalf of that amount

Total return.
You will be paid according to the final amount of coins earned over the whole experiment. 20 coins are equal to 0.075 USD, and the maximum amount you can win is 800 coins, equivalent to 3 USD.