Isn't it great that the car fleet is getting older?

Our initial reaction - made elsewhere - to this news was, well, that's obvious, isn't it? 

The average age of a car on Britain’s roads is at its highest level since the turn of the millennium with the proportion of motorists behind the wheel of an old banger surging.  

UK cars and vans in 2017 had an average age of 8.1 years which is believed to be the first time that the average age has been above eight since at least 2000.  

We've just had a deep and bitter recession, people will have been running their cars a little longer, not replacing them at quite the usual speed. As is always true readers in aggregate know more than any individual writer so it wasn't long before it was pointed out what good news this is, it means that cars are better, they last longer these days.

And then a very good comment indeed from "isp" (Ian P to those in the know):

In fact given the energy required to produce a car it could be argued that car efficiency has improved by more than you see from the simple mpg stats.

An important point - it takes energy to produce a car. If cars are lasting longer then that energy requirement for fabrication is being amortised over more miles and or years. The energy requirement for any one mile of travel is thus reduced. And reduced in a manner that we don't count in our normal statistics.

So far just an interesting observation. But now think of the near mania for scrappage schemes to get older cars off the road so as to increase the efficiency of the fleet. None of the calculations of these do include the energy costs of building the new vehicles - and certainly not in the case of electric vehicles and the energy required to make large batteries.

Those car building energy requirements are such that we don't actually know how much the mpg of the fleet has to improve for us to be gaining a net energy saving and we most certainly don't know whether scrappage schemes actually achieve a net saving - or, they might be energy sinks.

All of which leads to a more usual and much more important point. Planning of the economy is impossible because it's just too complex. What should we be including in our costs and benefits of any action? As Hayek pointed out, we can only use the economy itself to make such calculations. Nothing else does actually take account of these second and third etc order effects.