IF a new car doesn't fly out of the showroom the next version will be widely different - or simply not appear.
On the other hand, should it sell like hot cakes, expect Phase II to look surprisingly familiar. Daft to rock the boat if the punters love it, of course.
That approach has worked well for the likes of Volkswagen, most notably with the Golf (currently on v.7) and now Suzuki has followed the line of least resistance too.
So the latest edition of the Swift might be all-new on the outside but there's clearly been a case of evolution, not revolution.
Quite right too, you'd say after a drive in the new Japanese-built baby. The first one was right up there for its on-road credentials and the latest one is too.
It certainly keeps very clear roots with the first Swift, only gaining the bigger mouthed radiator look that is the current fad in styling studios around the world.
A tiny bit (10mm) shorter and (15mm) lower, the body is also wider (by 40mm) and by stretching the distance between front and rear wheels (by 20mm) there's a bit more legroom in the rear.
More crucially, because the size stopped some people signing for the earlier Swift, the newcomer's boot volume is up by a healthy 25 per cent, to 265 litres, and is now broadly in line with others in its class.
Prices now start at £10,999 for a SZ3 grade Swift powered by a 1,242cc petrol engine producing 89bhp and capable of a theoretical 65.7mpg average, combined with a 111mph top speed and 0-62mph in 11.9 seconds.
This same engine is available as the £15,499 SZ5 SHVS ALLGRIP - a string of capital letters telling us that the car has on-demand all-wheel drive (for ultra slippery conditions) and is fitted with a modest hybrid system comprising a small extra battery that powers a built-in starter generator and adds a whiff of accelerative power.
It also helps this model record the range's lowest emissions figure (97g/km), although April's car tax changes mean only a modest £20 first year saving over the car that's going to be the biggest seller.
That's a Swift with smaller three-cylinder 998cc engine that costs £12,999 in SZ-T guise and thanks to a turbocharger produces a healthy 109bhp and enough pulling power to provide a car that feels keen to get on with the business of moving you about.
There's been a modest weight reduction to an already lightweight car; you would need three of the slimmest 890kg version to tip the scales with a single Range Rover on the other side.
With the smaller engine up front the new Swift feels every inch ready to provide its 121mph top speed and sprint to 62mph in 10.6 seconds.
A modestly demanding hill route (with added Sunday cyclists galore) showed 58mpg on the dash readout - a fine result, if inevitably shy of the 61.4mpg official average.
A similarly demanding - and cyclist heavy - route in the 1.2 litre Swift dropped the readout to 52mpg; still good but from a car that felt less eager and engaging.
Rounding off the current Swift range (expect a hottish-hatch Sport along in the near future) is a 1.0-litre with automatic gears (£15,848) that tops the price list, or with the mild hybrid system (£14,499).
Suzuki has joined the single no-cost colour ploy that is making lots of cars look cheaper than they really will be. A non-metallic red is the only Swift finish that doesn't add at least £485 to the bottom line (with a metallic finish, or £650 if you want the roof a different hue).
Every new Swift has air conditioning and Bluetooth - and five-doors, as the previous three-door version is scrapped. Move to the SZ-T grade and you add smartphone link display, rear view camera, front fog lamps and alloy wheels.
Range-topping SZ5 Swifts have auto air con, satellite navigation, adaptive cruise control, polished alloys, rear electric windows and camera and radar that look ahead and will brake for you in an emergency.
Inside any of the new Swifts, hard plastics are order of the day with a blade of silvered plastic across the dash doing its best to raise the tone. Instruments and switches are easy to read and reach and Suzuki has not (thankfully) moved most functions to a touchpad screen.
So, a successful rebirth of a car that remains near the top of the class if you enjoy a drive.