A lesson for the incoming government - whenever we get one - on how quickly things can change, and be changed, in motoring can be gleaned from one, simple figure.
They just happen to apply to secondhand UK imports, but could dramatically affect so many other areas of motoring if decisive action is taken.
The Budget measure to impose a NOx tax on used imports (mostly diesels) has so far knocked back registrations of such vehicles by more than 27pc, according to the latest figures at my disposal.
Even allowing for pre-January 1 stockpiling of cars in advance of the tax coming into force and the subsequent lull in trade, it is a graphic illustration of effect following action.
Now we need similar decisiveness to impact in other critical areas quickly because the level of confusion among motorists (and indeed throughout the motor industry) about the medium-term future is not serving buyers or sellers.
A major decision this year will be for government to change the VRT system to take account of the tougher new WLTP emissions figures.
They could, if not accommodated by realistic new taxation bands, send car prices a lot higher in many cases.
Many instances of increases have already hit - under the current stop-gap transitional set-up.
It may be a complex matter but it needs urgent attention to help lift the fog of uncertainty around new-car buying in particular.
Parallel with that is the whole area of electrification.
As has been illustrated here in 'Motors' on several occasions over the past few weeks, motorists are being subjected to a lot of anxiety and confusion over what sort of car they should buy next - diesel, petrol, hybrid, electric - by lack of real action on several fronts.
It is generally agreed that thousands held off on purchasing to see what the outgoing government would do. Now we need to pick up speed with the next administration.
I am conscious of how easy it is to sound preachy and repetitive at times like this, but the obvious has to be stated.
We can't wait too long for the government to get up and going on how it wishes to manage the pace of the much-heralded drive towards more electric cars.
'Manage' is the critical word here because if the incentive is there we motorists will follow.
Just look at what the NOx tax achieved on imports in one fell swoop.
Surely a simple, fair, VRT series of tax bands to reflect a car's emissions in the WLTP era is not beyond us? It just needs to be seen to be fair (insofar as any tax can be described as such).
And surely setting interim goals - backed by strong investment in the infrastructure - for electrification is a matter of concentrating resources and energy.