SCOTLAND’S census has a “solid foundation” to build upon despite return rates being “lower than originally planned", a statistics expert has said.

Professor James Brown chairs an international steering group formed to advise the Registrar General on the quality of the census and the statistical approaches needed to get useful information from the survey.

He said: “While the overall return rates are lower than originally planned, NRS’s extension has improved consistency and returns across the country.

“With this solid foundation it is now time to move to the next phase and conduct a high quality coverage survey.”

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The professor of official statistics at University of Technology Sydney also said the extension had improved the quality of census data.

This supports Nicola Sturgeon’s claims at FMQs on Wednesday that the census would produce “credible, high-quality outputs".

The National: The census return rate is lower than for previous censusesThe census return rate is lower than for previous censuses

The census website still invites responses, showing you can “still avoid a possible fine” by completing the census by June 12.

NRS say the current response rate is 87.5%, nearly 2.3 million households.

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Some 28 of Scotland’s 32 local authority areas have achieved return rates of 85% or higher, and five of these have exceeded 90%. The 2011 census response rate was 94%.

Brown said: “With this solid foundation it is now time to move to the next phase and conduct a high quality coverage survey.

“The coverage survey, combined with innovative use of administrative data, will allow NRS to estimate the size, shape and characteristics of the population as planned.

“This will ensure the census estimates are representative of both Scotland as a whole and its local communities, as well as enable comparisons across the UK.”

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Registrar General for Scotland and NRS chief executive Paul Lowe said: “I am delighted to be able to draw on the expertise of Professor Brown and of such a distinguished group of statisticians and experts in census and administrative data.

“We have secured a good level of national census returns and coverage. I am pleased that the international steering group has acknowledged that we are in a strong position to move forward and I welcome the contributions they will make to steering our statistical and methodological work over the next few months.

“Our wide range of customers and users of census data can be further reassured that this support and advice from the steering group will help NRS to produce a high quality census data set – one that will ultimately provide them with the right statistical outputs they need to inform future service planning.”