- he didn't know enough about the variables in the real world to make them parameters in the model
- he could only take a punt about the interaction terms
- a more complex, realistic model would probably cause the computer to blow a gasket, suffer a melt-down or just get lost in an endless loop
The real world was sure to be far harder to manage because the spirit of free enterprise is alive and well out at sea. It is always in the fisherman's best interests to shoot one more net, if there was room for one more crannful or creelful of herring in the hold. The fact that the last scoop contains the last breeding male of a species is a regrettable, potential but unavoidable consequence of each ship managing its own best interest. This in the essence of the tragedy of the commons. Garrett Hardin's classic paper on the tragedy. Movie explanations: I - II=managed - III=economicspeak.
We're at the coal-face on the commons this year because of a change in Government policy about management of uplands. When we bought the farmlet where we live 20 years ago, it came with 1/20th part of the hill above the house which we owned in common with another 19 proprietors. Although we couldn't point to a single rock or sprig of heather which we owned up there, the total acreage was slightly more than the in-bye fields and pastures nearer the house. When we signed up for subsidies to help and encourage us to manage the land according to current EU farming policy, the check was effectively doubled because of the mountain commonage. Nobody wanted us to run sheep up there. Earlier subsidies of sheep farmers had given headage payments: an aliquotb of money for each unit of livestock each farmer owned. Particularly in the West, this resulted in over-grazing, habitat destruction, catastrophic run-off and landslips; the effects of which can been seen in the scarred landscape a generation later. Now, subsidy is contingent on running a certain amount of sheep up the mountain, for a certain number of months.
The sheep of each of the commoners who are signed up to the current scheme will all run together up there and each farmer will have to go periodically to look the hill and count his sheep. Seems like a waste of time if everyone does this separately if it could be done in common and in rotation. This cooperative arrangement was apparently agreed by a group of farmers from the other side of the mountain. But the latest gossip is that the arrangement has fallen through in bitterness and recrimination (with added dog poisoning to add spice]. One of the issues was that fact that only some of the commoners were signed up to the government subsidy and those who weren't were not limited as to the number of sheep they could run up on the mountain. It looked like the two competing groups were set for a collision course of mutually antagonistic interest. Needless to say the response to this was for everyone to stop speaking to each other. If I was in charge, I'd rip some of the suits from the comfortable desks in the Department of Agriculture and send them down the country to talk to the farmers (rather than at the farmers) and get the farmers to talk to each other.