The market price is assumed to stay the same, since
the new producer produces only a small fraction of the total
output.
In deciding whether the new technique is worth applying the
manufacturer looks at the
discounted prime cost= (prime cost + capital*rate of interest)/unit output
to see if it has fallen. It has from $52 per unit to $33 per unit
so it is worth using the new technique at the current rate
of interest.
The new production technique results in lower rate of profit
than obtained on the old technique, but it is more efficient
both in terms of labour input ( assuming input prices are
proportional to values ) and also in terms of discounted
prime costs.
If we assume that manufacturers are willing to adopt a
new technique if its discounted prime cost per unit is
lower than an old technique, then we could see the rate
of profit fall if the rate of interest was below the
rate of profit in a given industry.
> old new
const cap 100 270
dep 20 54
raw mat 10 10
wages 10 10
output physical 1 2
unit prime cost 40 37
unit price 70 70
profit 30 66
capital 120 290
rate of prof 25.00% 22.76%
discount rate 10.00% 10.00%
Interest paid 12 29 at 10%
profit of enterprise 18 37
discounted prime cost 52 33
I am very dubious about the whole concept of an average
rate of profit acting as a constraint on investment.
Rates of profit differ significantly between and within
industries, the nearest thing that firms actually
meet to an average rate of profit is the rate of
interest.
The latter is determined by the state rather than
by the rates of profit in industries.
Paul Cockshott