Here is a Tragedy of the Commons example
taken from a family history:
My uncle and aunt deeply believed that one should give their kids
all the chances they could to develop their talents. They have
two children (let's call them John and Anne, to keep the names
short) that fortunately for their parents are really gifted in
sports. John is a very good hockey player and Anne is an beautiful
figure skater.
Their parents always invested a lot of money for their kids to
progress in their respective sports. And as the caliber in which
they evolve involves more dollars, both John and Anne had to quit
the highly competitive level they reached.
The "Resource Limit" would be the total budgeted money
for sports (and - that's not in the archetype, the family was
blowing it year after year). The "Gain per Individual"
would be the dollars budgeted per activity (hockey vs. figure
skating). The "Total Activity" could then be the total
money spent on sports by the family.
Now, say A is John and B is Anne... A's gain could be John's practice
of hockey, which, as the competitive level increases, gets more
and more expensive (travel, more equipment...I guess this would
be shown in the arrow going from "A's activity "- competitive
level - to "Total Activity"). Another point is that
as John perseveres in playing hockey at better levels, he gets
better at it, and wants to play more --- Reinforcing loop...
The same could be said about Anne's gain is Anne's practice of
figure skating, which increases as the competitive level increases.
She's getting better and better, wants to practice even more,
and cost goes up (again, an element between "B's activity"
and "Total Activity") as now on top of a coach, she
needs a choreograph and to rent an ice rink for herself...
This is how the story ended.
As the parents could not find sponsors for Anne (a friend of hers
told me she would be good enough for the National Team) and since
no such thing exists for individual hockey players (at least not
too easily in Canada), money dried up. They already had taken
a second mortgage on the house, my uncle had found himself a second
job...
The day of their parent's 20th Anniversary, the kids announced
their parents they were both quitting the competitive side of
their sport - Anne became coach herself, and John left home to
go to university. This was originally a shock to the parents,
but after a while, all the family recognized it was the best thing
to do...
Anne and John's talent didn't bloom in sync. At one point, when
it became apparent that Anne was really gifted for figure skating,
John was just an "above the average" hockey player.
It was time to take a decision for Anne's future - hiring of a
choreographer, big expenses to be foreseen. Their parents took
a fair decision to make sure both of their kids had access to
similar resources (money) - that's when the second mortgage was
taken on the house - and John was sent to a special hockey school.
That year, he quickly became the best player in his league...
They might not know, but by avoiding to go in a "Success
to the Successful" archetype - all the sports budget could
have been used by Anne, they got caught in the Tragedy of the
Commons...
Many thanks to Christian
Giroux, Montreal Canada for submitting this example.