> [..] it signifies the level of performance that uses the least amount of inputs to achieve the highest amount of output. It often specifically comprises the capability of a specific application of effort to produce a specific outcome with a minimum amount or quantity of waste, expense, or unnecessary effort.

to quote wikipedia quoting Sickles, R., and Zelenyuk, V. (2019). "Measurement of Productivity and Efficiency: Theory and Practice". Cambridge: Cambridge University Press.

Offering that criticism without clarifying what efficiency measures in your opinion doesn't allow us to follow your viewpoint without us just taking your word for it. Needless to say this isn't considered good style in a discourse.

A 100 percent "efficient" system can be one that is overfitted to certain metrics and it is the typical death sin of management to confuse metrics with reality and miss that their great numbers hollow out anything that makes a system work well and reliable, because guess what: having 1 critical employee and working them like a mule is good when things work, but bad when they suddenly don't, because that second employee you thought was fat that could be cut, was your fallback. In that case your metric of efficiency was slightly increased while another, less easy to quantify (and therefore often non-existent) metric of resilience went down significantly. This means if your goal was having an efficient and resilient company, but your metric only measured the former, guess what.

Same is true in engineering, where you can optimize your system so much to fit your expected problem, one slight deviation within the problem now stops the whole thing from working alltogether (F1 racing car when part of the track turns out to be a sucky dirtroad). Highly optimized systems are highly optimized towards one particular situation and thus less flexible.

Or in biology, where everybody ought to know that mixed woods are more resilient to storms and other pests, while having great side effects for the health of the ecosystem, yet in pure economic terms it is easy to convince yourself the added effíciency of a monoculture is worth it economically, because all you look at is revenue, while ignoring multiple other metrics that impact reality.

My take was that initially the metric is appropriate, but then with overfitting, it’s not enough.

It eventually becomes a bad proxy metric.

The argument is that regardless of what metic is chosen, it'll create deminishing returns followed by negative returns.

What it means is the objective can't be static - for example once satiated, you need to pick different one to keep improving globally. Or do something else that moves the goalpost.

Accusing these examples of involving "bad proxy metric" is identical to the no true scotsman fallacy.

Might need to read some Goldratt. We generally don’t understand efficiency that well.

Yeah, every single example listed looks like gaming of bad metrics. Framing it as overfitting is unproductive, IMHO, and discounts the essentially adversarial context. I also discounts the stupidity of equating "efficiency" with a high score on a simple metric. Reality has a Surprising Amount of Detail, and all that.

gaming of metrics. Not of bad metrics. The point is all metrics will become bad because they will be gamed for.