Engineers are great testers. They like to build scale models and carry out tests. Non-destructive tests, destructive tests, wind tunnel tests, tensile strength tests...if you can wonder about it…Engineers have a test for it. Have you ever looked at a computer magazine? That's Engineers at work. Testing everything that moves…comparing this test with that test. Have you ever looked at the car magazines? Engineers again. Road tests, tyre tests, brake tests. Test. Test. Test.

Not so the Economists. The only tests they do are full-scale tests. Even the Military play a War Game or two before committing themselves to the real thing. Not that it helps much. Perhaps they should start stimulating disaster?

Professor Jay Forrester at MIT was one of those who pointed out the foolishness of this. Forrester tried to do what Engineers do. He didn't think up a theory and model it mathematically and call that Testing. He went out into the Real Economy and found out what people with real economic power were actually doing. He then went back to the lab and tried to build a computer model that would simulate various aspects of their behaviour.

After several years work and several thousand modifications to his model of the US economy, he went back out into the real world and spoke again to key players in the US economy.

'Tell me again what you do when you get this or that piece of information?' he would ask them.
'Well,' they would reply, 'Funny you should ask, because I used to do this, but now I do the opposite.'
'Fine.' Professor Forrester would say. 'Bear with me a moment while I just check this fuse. There. That's programmed in now. Let's see what happens. First we'll do what you used to do.'
'Well, goddam it,' would come the reply...Jimmy Carter was in the White House at the time so there were a lot of Southern drawls around Washington...'That's what the son of a bitch did. Would you believe it? Say, how come your box of tricks managed to do that? What sort of Economist are you, anyway? What's it doing now? Yeah. That's it. That's the way we like it? What d'yer do? You did what I do now, huh? Well I'll be damned!'

Forrester met this reaction so often that he coined the phrase the counter-intuitive behaviour of complex systems to explain what was going on. Soon they were asking him to bring his magic box to their Senate Committee Meetings.

'There's nothing magic about it,' he would assure them. 'I ask people what they're thinking of doing and the computer tells me the sort of things that will happen if they try it. I figured it makes more sense, costs a lot less money and gives you more precise answers a lot quicker than putting Legislation through Congress and testing a policy out on 250 million Americans.'
'Damn right! Why that crazy son of a bitch...'

And of course the bigger your economy, the more people will be engulfed by the main effects, the side effects, the after effects and all the unanticipated unfortunate effects of this Full-Scale Testing.

The Euro is unprecedented. Full-blown full-scale testing...of untested theory. Lunacy for short. But before you rush off to ask MIT to build a simulation model for the Euro there's one more thing you should know about Model Testing.

Engineers have discovered there's a lot of art and quite a bit of science to Scale Testing. You can't scale back your car to a sixteenth the size of the full-scale version and shove it in a wind tunnel. Or rather you can…but you'll get the wrong answers. You have to scale down in a way that reflects relationships between Cause, Model and Effect. Volume Effects for instance tend to be 'to the power of three'...Area Effects 'to the power of two'.

Twenty years ago Kirkpatrick Sale wrote a book entitled Human Scale. He didn't know anything about Scale Testing. But he knew why giants don't exist. Their legs could never support their weight. The strength of a giant's leg would obey a square law...the area of the bone's cross section. But the giant's weight would obey a cube law being proportional to volume. Six foot turns out to be quite a sensible size for a creature like man. Giants would crush their legs with their own weight.

Sixty years ago D'Arcy Thompson had reached similar conclusions and become intrigued by their implications. He explained his thinking in a book entitled Growth and Form.