Over on the Long Tail blog I found a fascinating fact about the render times of Pixar movies: In 1995 each frame of Toy Story took two hours to render yet in 2005 an average frame of Cars took 15! One commenter remarks:

If I remember right, [Tony De Rose's] first project at Pixar was to work on a system to simplify/accelerate the "rigging" of control points for facial features in 3d models. What he found was that every improvement he made in simplifying facial animation was being used by the animators to adding more precision and detail, rather than to reduce the amount of time required to do the facial animation.

And another:

I've also heard that the time to get from midtown to downtown Manhattan has remained constant (~45 minutes) for the last one or two hundred years. The increases in transportation technology just allow the city to pack in more density.

Which reminds me of the traffic speed in London:

Despite the congestion charge, traffic in central London moves at just 10mph - the same speed as horse-drawn carriages a century ago.

Average traffic speed has improved by only 1.5mph since the toll's introduction in 2003, mayor Ken Livingstone has admitted before the London Assembly.

That means cars in central London now travel at the speed of a running chicken, instead of a running house mouse.

It seems to me that there's a general principle at work here which creates an equilibrium between forces. In the Pixar case it's the opposition of cost, quality and time that makes the render times rise rather than fall. With traffic it's time versus convenience. In physics we have the ideal gas laws that constrain the temperature, pressure and volume of a gas (which explains why aerosol sprays come out cold and hot air balloons rise).

The gas laws define a strongly constrained system (change the volume and the pressure or temperature has to change to compensate) but the Pixar and traffic systems are weakly constrained - there's some give in the system.

With limited capacity or capability people naturally make compromises on their usage of any particular resource. Back in 1996 the Pixar artists pushed their cost and time resources to the limits to get the best quality and the same is true today but the budgets have increased. Each system seems to have a natural equilibrium point - the traffic in London will always move at the speed of a running chicken because that's the minimum speed commuters will tolerate. I wonder if there are any equilibrium systems in the web?