One of the dominant trends in the car market over the last 10 years has been fragmentation – the increasing proliferation of 4x4s, MPVs, coupé-cabrios and their ilk.

The general assumption has been that, as niches proliferate, the traditional bodystyles will inexorably lose share.

However, and rather surprisingly, it has not all been one way traffic.

It is true that hatchbacks have lost market share since 2001 (from 61.8% to 59.5%), but that is a very small decline given the number of new alternatives which have emerged.

In fact, some of those alternatives are themselves now in decline.

Like a Catherine wheel, the coupé-cabrio market burned brightly for a few years and then started to fizzle out.

With products that were expensive, heavy and frequently rather ugly, there was a precipitate decline once the initial novelty had worn off.

At least some of the models introduced in the last few years will not be replaced when they come to the end of their production runs.

Perhaps more surprising is the fact that MPVs have declined, given the entry of so many more competitors, particularly in the C-MPV (Zafira class) and B-MPV (Nissan Note class).

In the C-MPV segment, share has declined sharply from 24.8% in 2006 to 17.0% in 2011.

Partly, this is model-related as the best-selling Vauxhall Zafira is close to the end of its life, but it also shows that upward trends do not carry on forever.

Even in the B-MPV segment, where there has been a lot of model activity (e.g. Citroën C3 Picasso), the MPV share has only grown from 8.0% to 10.8%.

The most unlikely fact is that the humble estate car, which was thought to be easy meat for MPVs, has actually risen fractionally over the whole period.

Clearly “established” is not the same as “old fashioned” when it comes to segmentation.

Across the whole market, there is only one segment which has been true to type over the last decade.

Saloons, on the decline ever since the 1970s, have continued to lose ground.

Most of the decline has been in the upper medium segment, where saloon share has declined from 27.3% to 16.6% since 2001 – if people want a big saloon today, they are probably going to want an executive badge to go with it.

This volatility presents a major challenge to the car manufacturers.

Identifying emerging trends is hard enough, but they have to think increasingly about whether a new niche is going to last long enough to make designing a new car worthwhile.

Alternatively, is that new trend they have just spotted the next SUV segment – the part of the market that has been growing steadily for 20 years?