In order to give the word "efficiency" any meaning whatsoever, you have to define the context in which it is being used. The picture above provides quite a good example, precisely because its relevance to efficiency is not immediately clear. 

My wood-wallah sells wood in 1-metre, 50 cm (19 inch) and 30cm (12 inch) lengths. I normally buy 30 cm logs. They vary widely in diameter, from maybe 50mm (a couple of inches) to about 25cm (10 inches): rarely more. Although I can perfectly well burn the thicker ones, I quite often prefer to use thinner ones. This means that sometimes, I need to split the fatter logs. I used to do this with an axe, but lately I've taken to using a wedge (which you can see stuck in the log) and a sledgehammer (which you can see resting on the log). I find this quicker, easier and more accurate than using an axe. Most people would regard this as more efficient. 

There is however more to the story (and to the definition of efficiency) than this. You can just about see that the log I'm splitting in the picture above is a bit lumpy or gnarly. This is because it is far from straight grained. It's much easier to split straight-grained logs: three or four blows with the sledge-hammer often suffice. Gnarly ones are a lot more difficult: I may need ten or twenty blows, or more. It would be a lot easier to burn them whole, and to split only the straight-grained ones. So why would I choose a gnarly one?

Because part of the reason I split wood is for the exercise. If I have to keep lifting and bringing down the hammer; if I keep having to knock the top of the wedge sideways, to re-align it; if from time to time I knock the log, with the wedge embedded in it, off the chopping block on which I cut it (the only reason it is on the log pile as shown here is artistic license), so that I have to have to pick it up and replace it on the block; well, that's more exercise. I just don't need as many split logs as I could easily make with the straight-grained ones, so from the point of view of exercise, the slower, more difficult logs are more efficient. The two definitions of "efficiency" are pretty much diametrically opposed. 

There are other potential dimensions to efficiency. A hydraulic log splitter would be more "efficient" still, in that I could do more work, faster. But hydraulic log splitters are quite expensive; they require maintenance; if I bought one, it would take up space I could better use for something else; and I just don't need that many split logs. This makes the hydraulic splitter quite inefficient from my point of view. That's before you even consider the fact that I quite enjoy ten or twenty minutes of splitting logs.

Similar arguments can of course be applied to other value judgements masquerading as scientific verities. Ergonomics, for example. I find it far easier, more convenient and more intuitive to use an old-style aperture ring on a camera lens than to use a thumb-wheel somewhere on the camera. This suggests to me that the aperture ring is more ergonomic. The Chartered Institute of Ergonomics and Human Factors quotes the International Ergonomics Association on their web-site,

Ergonomics is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimise human well-being and overall system performance.

Even so, I have been assured by someone whose opinion I normally respect, that what I find better isn't really more ergonomic. I just think that I find it easier, more convenient and more intuitive. He knows better than I what suits me, and according to him, I'm wrong: the thumb wheel is more ergonomic. This is the kind of one-size-fits-all thinking that drives me up the wall. Ergonomics, like efficiency, is contextual; and anyone who fails to understand this is missing the point of both. 

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Picture and text copyright (c) Roger Hicks 2017