An article in the FT suggested that changes to the way ONS conducts its surveys of construction might have caused respondents to submit data referring to too early a reference period.
Siobhan Carey wrote to clarify the issue and set out the ONS view that these changes would not have caused respondents to reply differently.
Your article, ‘Builders say ONS numbers do not add up’ (FT, 9 May 2011), needs clarification. Up to 2010, there were two construction surveys - a monthly new orders survey and a quarterly output survey. From 2010 there are still two surveys but the output survey is monthly and the new orders survey is quarterly. It is the results of the output survey that are used for the construction element of GDP. The monthly output survey provides more timely estimates of activity than were available from the previous series.
Paragraph two states that '...change to the methods... led companies to submit data about business completed up to six weeks earlier’. ONS believes that there is nothing inherent in the new ONS survey that could change respondents' behaviour in this regard. The questionnaire was tested with a range of businesses during the development of the new survey.
Paragraph eight refers to '...construction orders for February'... As mentioned, the orders survey is now quarterly and quarter 1, 2011 results have not yet been published. The new orders survey results are not used in GDP calculations.
In summary, the Office for National Statistics has been carefully monitoring the performance of construction statistics, as we do with all our statistics. We routinely evaluate the performance of all our outputs, and we have no reason at present to believe the construction series is giving a distorted picture of what is going on in the sector. The new surveys introduced last year were a major improvement on what went before. We have no evidence of a change in the way respondents complete returns. We will consider the need to make adjustments and improvements to the methodology, should this prove necessary.
Deputy Director, Economic Surveys Division
Office for National Statistics