Comment by mlyle
> I wasn't talking about "base metals and relatively simple manufacturing". Were you?
A whole lot of the decline that we're talking about has been in those sectors. Microchips and aerospace grew; simple consumer goods and steel manufacturing fell through the floor.
> The behavior of markets assumes free choices by participants t...
Incentives can be, and often are misaligned. However, the context of our discussion is talking about large overall economic growth that has outpaced manufacturing growth, even though it is still positive. This isn't evidence of misaligned incentives.
> In your unit 3, do you draw LRATC curve as a parabola? Because that's the wrong shape for manufactured goods.
It's absolutely a bathtub.
It's steep-downward sloping, mostly flat for a loooooonnnggg time, and then upward sloping. Indeed, this understanding of the shape of LRATC originally comes from study of manufactured goods. At some point coordination gets hard and further increases in quantity require using resources that are not well suited for the task.
Of course, the quantity at which costs slope upwards may be at an impractically large quantity for any industry-- in which case that industry is likely to be a natural monopoly. And there are some recent arguments that coordination is easier thanks to information technology and that it is even harder to reach diseconomies of scale.
> It's absolutely a bathtub.
I endeavour to convince you that you are teaching your students a falsehood. Natural resource industries have bathtub-shaped average costs. Average costs fall strictly monotonically for manufacturing, and marginal costs either fall or remain constant. Constant marginal costs are what you get if you don't even bother to solve coordination problems, and just copy-and-paste your whole assembly line instead (except even then you can't help but gain economies of scale, if only from your tooling suppliers). The misconception that it's a bathtub does not come from the study of manufactured goods, it comes from thought experiments about manufactured goods done by people who never managed quote requests at a real factory. Empirical studies done on actual firms almost never show rising marginal costs at any quantity.
That this error has permeated introductory economics is a very, very big problem.