The point that Andrew was making was founded on what is in
essence a simple observation - that capital exists as a stock
and thus any technological change that results in a cheapening
of the elements of constant capital must result in a loss on
the capital account, which, if the technical change is continuous
must itself lower the rate of profit.
This may be cast in a variety of different equations, but
the insight remains the same and must have been independently
arrived at many times. I recall it being current in discussions
at the CSE over 20 years ago.