§ Mr. Gwilym Robertsasked the Secretary of State for the Environment (1) whether the figures he gave to the hon. Member for Cannock on 9 March, Official Report,c. 384, for the number of cavity wall insulation installations in Great Britain for 1978 and 1979 included all such installations carried out in both the public and private sector during those two years;
(2) whether the measurement techniques used by Audits of Great Britain to provide figures for the number of cavity wall insulation installations in Great Britain, given to the hon. Member for Cannock on 9 March, Official Report, c. 384, had altered for the year 1980 from those used for the two previous years.
§ Sir George YoungThe figures are estimates of the total of installations of cavity wall insulation in Great Britain in existing public and private sector dwellings; numbers of installations in new dwellings during construction are not available.
The basic techniques used by AGB were the same for all three years, but minor amendments to the questionnaire in the third quarter of 1980, may have resulted in more complete reporting by tenants of installations by their landlords. The effect is likely to have been very small, in relation to sampling errors and year-on-year changes.