Following on from the recent AM article about the proliferation of models and options, I came across a list showing the bewildering variety of Rover 75 versions.

There must be almost as many versions as sales last year and this got me wondering how many sales per version would be considered normal by carmakers.

After a bit of digging, some curious figures come to light. At one extreme are the big volume models like the Focus: this sold 102042 units in the 11 months to November 2004 and 116 versions have been listed during that time. The result is 880 sales per version, which is around what you might expect. Close to 1,000 sales per version per year seems a reasonable number for a big-selling car.

The equivalent figure for the Mondeo (similar number of versions, but smaller sales volume) is 362.

At the other extreme you might expect to find the BMW 3-series. BMW is well known for being better than anyone else in Europe at the flexible manufacturing of huge numbers of variants.

The public knows BMW is a success because of its products and its marketing, but its manufacturing know-how is just as important. There have been 173 versions of the 3-series on sale in 2004, giving an average figure of 112 sales per version.

That is not a problem for BMW: its factories can cope (even if its dealers may struggle with the variety) and margins are higher than most.

What of Rover, which is where we came in? The Rover 25, which has had its model range pruned, seems not too bad at 210 sales per version – until you discover that the average figure for superminis is 751.

The Rover 45 is poor by any standard at 105 and the Rover 75 is terrible at just 86 sales per version. Given that most Rover sales are in the UK, the average worldwide for the 75 cannot be much over 100. How can it be worth having such proliferation in a relatively low margin model?

If you are wondering how the latest model extensions are doing, combined UK sales of the 4.6 and the Limousine have still to hit 50 units.

The average version of an executive model has sold 123 units – apart form the halo models like the M5 and AMG, can those versions selling 50 or 60 units really be justified? It may be time for the bean-counters to have a word with the marketing department.