2. Letter from Dr Stephen Hickey,
Department of Transport to the Chairman
VEHICLE EXCISE
DUTY EVASION:
2007 ROADSIDE SURVEY
RESULTS
Thank you for your letter of 26 February.
Can I first express my regret for any embarrassment
which the latest results have caused to the Committee; and reassure
you that neither I nor my colleagues had any advance knowledge—at
the time of the October hearing or indeed until very shortly before
the 2007 results were published last month—that the increased
use of camera checks in the last survey would reduce the estimates.
Nor did the statisticians, who were able to use the new camera
data to introduce additional quality checks.
As you know, the survey is very large, involving
as it now does around 1.7 million vehicles. Matching the data
collected at roadside to the information held on the vehicles
database is therefore an important and difficult challenge. As
we mentioned when we appeared before the Committee last year,
we have been moving increasingly away from manual data collection
(where individuals write down number plates) to video (through
the use of cameras). We did not foresee the effect that would
have on the 2007 results nor that it would show that for past
surveys the evasion rate may have been erroneously inflated.
I attach a detailed note setting out the reasons
for this effect and the (lengthy) quality assurance process by
which it was revealed. You will see that the main reason for the
change was that the greater use of cameras enabled a new, and
previously impractical, level of quality assurance; but that the
effect of the more comprehensive and detailed checks was "asymmetric"—reducing
a cause of inaccuracy which we now realise had previously tended
specifically to inflate the estimates.
I would like to make clear that at no point
did we withhold any information from the Committee. When we appeared
before you, we had no reason to think that the improvements to
the 2007 survey would result in such a change in the evasion estimates.
The statisticians similarly had no reason to anticipate that the
use of visual images to undertake a new level of quality assurance
would reveal a bias in previous survey estimates.
Nor could we have contacted the Committee in
advance of publication. As you will know, the National Statistics
Code of Practice includes a condition that statistics are not
divulged before their official publication—and neither officials
nor Ministers are made aware of the results until a few days before.
As soon as public discussion was permissible, on the morning of
14 February, Jim Fitzpatrick did try to contact you, but this
did not prove possible beyond his leaving a voicemail and a text
message. At official level we did, of course, contact the NAO.
I should also say that, although it now appears
that previous results have inflated evasion, it remains the view
of our statisticians that the pattern, and hence increases and
decreases in evasion, are correct. It is therefore likely that
there was indeed an increase in evasion from 2004-06—so
the Committee's recommendations remain pertinent and we intend
to act upon them.
I apologise for the difficulties the latest
results have caused for the Committee. It is particularly unfortunate
given that they represent the most accurate data yet produced
on this complex but critically important issue. I very much hope
that the improved survey will continue to provide a sound evidence
base for our strategy in the future.
I hope this is helpful. If you have any further
questions on the way in which the survey was carried out and the
way in which the results were published I would be more than happy
to answer them.
I am copying this letter to Robert Devereux
and to the Comptroller and Auditor General.
7 March 2008
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