On the first Monday of every month, a bunch of my friends get together for dinner. The gathering can be as small as 3 or 4, but often exceeds 10 attendees and includes people who don't show up to most of our other gatherings. Ted and Mikey, who started this tradition, developed an interesting and surprisingly effective set of rules for getting a herd of geographically disparate people to converge on an arbitrary location at an arbitrary time.

  1. An email list is assembled with everyone who might conceivably want to attend the event.
  2. On the morning of the big day, someone sends an email to someone on the list, asking them to pick a restaurant and a time to meet.
  3. That person indicates their selection by replying to the list.
  4. Anybody may veto the selection, but must provide an alternative selection.
  5. Any number of vetoes may happen before a selection remains unchallenged.
  6. A person who proposed a selection that was vetoed may not later re-propose the same selection in a veto of their own.

For logistical reasons, vetoes are cut off and a final selection must be established by around 4:30 or so. Messages do cross in the mail (for instance, two people may be invited to choose by different participants simultaneously), but this rarely causes any problem. Vetoes are also rare. The chosen person may pass and not make a recommendation. In this case, it is considered polite to designate another person to make the choice. If the chosen person doesn't respond in a timely manner, the process may restart with someone else.

For these large monthly meet-ups, people usually just pay for their own food. But when the number of participants is small (5 or less, for example) and fairly constant, and the number of occasions is greater (weekly, for example), there is a more interesting approach. Everyone tosses a coin to see who will pay for dinner. There is a set of rules for this, too.

  1. If there are two participants, one tosses a coin and the other calls it.
  2. If there are more than two participants, everyone tosses a coin.
  3. The majority (composed of the greatest number of people who got the same side up) drop out.
  4. If the two sides are exactly equal in number, then everyone tosses again.
  5. The previous rules iterate until only one person is left.
  6. That person pays for dinner for everyone.

If the pool of people participating in this scheme is relatively uniform (most of the same people most of the time), then the random process all but guarantees that in the long run, this will average out to everyone paying about the same. It's different from a typical lottery in that there's only one loser and everyone else is the winner. But it's the same in that, in the end, no one stays rich.