References to the JDPower Customer Satisfaction Index prompted me to go and read the report on the Whatcar website, at www.whatcar.com/News_SpecialReport.asp?NA_ID=20780...3

It's intersting reading, because the data seems to tell a very different story to the press coverage.

Here are some of the observations I made about the data:

1/ All cars score very well

* The highest score is only 88.4% (for the Honda Jazz), so even the best model still has quite a few failings.

* The lowest score is 69.3% (for the Fiat Bravo), so even the worst result is far from abysmal.

When I was at university, an exam mark of over 70% was graded as a "first". If we apply that grading here, even the worst result only narrowly misses the top grade. Second-last place goes to the Renault Espace on 72.8%, which is a clear first-class ranking.

The best cars get very similar results

The top ten cars have ratings so close that they are probably within the margin of error.

First placed car, gets 88.4%; tenth-placed gets 84.1%. Considering that these are figures based on subjective measurements, I wouldn't let that small a difference influence my purchasing decision.

3/ The top 50% of cars are very closely bunched

The first placed Honda Jazz gets 88.4%, the joint 60th-placed Vauxhall Omega 80.0%. That's probably outside the margin of error, but it's not a huge difference: the Omega is probably less satisfying, but not by much very much. If the ratings are accurate, the difference is unlikely to spoil your day.

(Conversely, if the Omega really is a bad car, then the ratings system does not reflect that)

4/ Whatcar's star-system may be misleading

Take superminis. First placed Honda Jazz on 88.4% gets five stars, as do the second-and third-placed cars on 85.x%, but the four-star Hyundai Amica gets a very close 81.9%. The two-star Fiat Punto is very close to the Amica, on 77.3%, while the in-between three-star Citroen C3 gets 79.4%.

With scores that close, the Amica, C3 and Punto really deserve to be in the same bracket ... but instead, the Amica appears to do twice as well as the Punto. I wouldn't use this star-system as a guide.

Conclusion

I don't know enough about how JD Power builds its ratings to really judge how useful the scores are. But if we assume that they are a reasonable measure of something, then far too much attention is paid to them -- because they basically paint a picture of manufacturers achieving broadly similar outcomes.
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