The Tragedy of the Commons

	[(C) 1997 Loren Petrich]

	There is an interesting paradox of resource management that was 
pointed out by biologist and environmental activist Garrett Hardin in the 
1960's, called the Tragedy of the Commons. It was intended to explain 
such disasters as:

* Overgrazing, overhunting, overfishing
* Traffic jams
* People crowding to get on or off of multi-occupant vehicles such as 
buses, trains, ferryboats, and airplanes.

which go against the self-interest of all those involved. The answer lies 
in the difference between individual and collective self-interest, as 
will be explained in the following examples; individual self-interest can 
work against collective self-interest. I will also explain a related 
concept, "externality", where the cost of one individual's activities are 
borne by another.

	The examples I choose have been selected to be down-to-earth and 
ones that myself, at least, can relate to. I choose them because I do not 
wish to demonize Big Business, as too many environmentalists are prone to 
do, and because they may reflect the direct experiences of many of this 
document's readers.

	In my first example, imagine that you and your friends like to go
to parties in a park, and that you like living behind all your beer cans
and wrappers and whatnot. And imagine that lots of other people like
having parties in that park, and that they also like to litter. Why? 
Because to each individual or group, the cost of not littering is greater
than its benefits; the cost is borne by each individual, but the benefits
are not, being more diffuse. 

	In my second example, imagine that you are one of the users of a 
multi-user computer system, and that you and the others like to use lots 
of CPU time, disk space, printer paper, and other such resources. You 
figure that the cost of restraint in CPU and disk usage is greater than 
the benefits, and so you try to use as much as possible. The others make 
the same calculation, and the CPU gets loaded down and the disks full.

	What can be done about it? In a way, the ideal solution would be 
to have a world of virtuous anarchists, who would not litter or use too 
much CPU time or disk space. However, that is not practical in many 
cases, especially if there is money to be made from misbehavior. 
Furthermore, those who try to be virtuous will get very annoyed by those 
who are not, especially if such people practically thumb their nose at 
the idea of being responsible. Exhortations to be virtuous will not be 
well-received if the exhorters appear to be looking the other way at 
certain misbehavers, as sometimes happens. A vigilante approach would be 
to personally come after the litterers, CPU hogs, and disk hogs, but that 
can degenerate into civil war.

	One often-proposed solution to the Tragedy of the Commons is
splitting up the relevant resource. Though practical for some resources,
it is not necessarily practical for others; attempting to do so may
destroy the resource or may even be physically impossible. In the case of
the park, dividing it up would leave all its would-be users with not much
park. In the case of the computer system, one way out is to acquire a lot
of personal computers, each one for the use of one individual. For a
multi-user system, however, the CPU is not easily divided up, but the
disks are. A sysadmin can easily assign disk quotas to all the users,
which are enforced by the computer's OS. This dividing up of resources can
be done not only in space, but also in time; in the case of the computer
system, use of the computer is divided up among the users automatically by
the OS, as it switches between the various users' programs. 

	The mention of the sysadmin suggests one solution to this
conundrum: government regulation, the sysadmin(s) and the OS being the
government of the computer system. Note that I mean "government" here in a
very general sense, that of a central ruling authority; a private owner of
the whole resource is a government in this sense. Also, the splitting-up
solution sometimes has the problem of how it is to be enforced, which
often leads to a convergence on the sysadmin approach. This approach,
however, is not without its problems, however; these include bureaucracy
and efficiency of enforcement, not to mention concentration of power and
questions of favoritism and fairness. There are those who claim that all
the sysadmin has to do is set appropriate prices or allow the users to buy
and sell resource rights, but that is just another version of the sysadmin
solution. 

	Now we tackle a related problem, that of externalities, which are 
side effects of one's activities that are borne by others. These 
represent another example of how self-interest can have troublesome 
consequences.

	In the park example, externalities result if one plays loud music 
or if one dumps one's garbage into a stream running through that park. 
The music may annoy the park's neighbors, and the garbage may float 
downstream and accumulate onto a tree that has fallen into the stream, 
creating an eyesore for those near that fallen tree. In the computer 
example, externalities result if one is doing something that gets in the 
way of someone else doing something -- if one is running some big number 
cruncher or disk accessor at a high priority, it will slow down 
everything else, because with the priority it is run at, everything else 
will have less time than in the absence of it. For example, if one is 
playing a game that does a lot of calculating or screen updating, and 
one's gameplay does not require instantaneous response, then some delayed 
action will be tolerable. However, others who are doing some text-editing 
(say) will get very annoyed, since the system does not quite respond in 
real-time fashion, and this is typically _very_ annoying to those who are 
trying to edit text.

	Just as before, there are ways out. One would be for the park 
neighbors to gang up on the loud-music players, and for the text-editor 
users to gang up on the CPU hogs. Another way is illustrated in the 
computer example; the sysadmin can arrange that the OS give lower 
priority to those jobs discovered to be CPU hogs; they can be reduced in 
priority to allow users wanting fast response while text-editing (usually 
not a big CPU hog) to have it.

	If there is any lesson to be learned, it is that such phenomena 
as overhunting, overfishing, resource depletion, and pollution need not 
be caused by any special depravity on the part of Big Business, but can 
easily be caused by individual-scale self-interest causing trouble on a 
larger scale.