The registration system change from an annual August phenomenon has eroded plate premiums.

Or has it? It’s always useful to challenge assumptions, so we looked at today’s plate premiums and compared them with those found under the old August letter change.

Working from a July 2004 Black Book valuation we looked at one-year-old cars on three plates, at eight mileage points, going back to 02 52. Our supermini sample comprises Peugeot 206, Renault Clio, Vauxhall Corsa and Ford Fiesta. In the executive sample are 2.0-litre variants of Audi A4, BMW 3-series, Mercedes C-class and Lexus IS saloon.

Although there is a marginally larger premium identifiable in the supermini sector, this is not statistically significant and may well disappear with a different sample. For the superminis we found that the 03 03 sample basket, at 20,000 miles, carried a premium of 3.8% over 03 52.

In the executive sample we found the premium stood at 3.5%. Looking at 03 52 compared with 02 52 the difference for superminis was 2.9%, while the premium in the executive sector stood at 2.5%. This clearly points toward further investigation into the difference between the plate and the year change to confirm what appears to be more significance in the plate letter change rather than the year change.

We then went back to October 1998 values for 97R, 97P and 96P cars at one-year-old, with 20,000 miles. This sample comprised Ford Fiesta, Renault Clio, Peugeot 106, Nissan Micra and Citroen Saxo in the supermini sector and Audi A4, BMW 3-series and Alfa 164.

A premium of 8% for the letter change and around 6% for the year change was identified in the super-mini sector. For the executive sample the letter change brought a 6% premium and the year change, just over 3%.

When the old and the new premiums are collated we begin to see that premiums are more similar now to those found under the old system than is commonly assumed.

Although the supermini premiums are indeed lower under the current system, according to this limited sample, that relationship is reversed in the case of executive cars.

To make real comparisons we have taken one plate and one year change for the old August-to-August system and two plate changes, plus a year change, for the new system. It’s a limited sample for a firm conclusion, but the indications are that premiums have changed little over the past seven years on an annualised basis.