New Data: Transforming how we count the population

Statistically Speaking

In this episode we discuss how the ONS has been working to transform the way we count the population, using new datasets to give more accurate, timely, and detailed measurements.

On 29 June 2023, the ONS will be launching a public consultation on its proposals for a transformed population and migration statistics system. Understanding user needs will be essential evidence in making its recommendations to Government on the future of population statistics.

More detail available at: www.ons.gov.uk

To explain more about the public consultation, and answer your questions, the ONS is holding a series of free events in July 2023:

• National Statistician’s launch event, London, 4 July 2023. (Online attendance also available)

• National Statistician’s launch event, Cardiff, 6 July 2023. (Online attendance also available)

• Launch webinar, 13 July 2023. (Online only)

You can also watch our transformation journey video, which is also available with British Sign Language (BSL), and in Welsh, with BSL.

TRANSCRIPT

MILES FLETCHER

Welcome again to ‘Statistically Speaking’, the official podcast of the UK’s Office for National Statistics. I’m Miles Fletcher and this time we're looking at the future of our population statistics. How best to count all of the people, all of the time, and provide the most valuable information on changing characteristics that can drive excellent research and sound public policy. All of that is the subject of a major consultation exercise that's running during the summer of 2023. It's all about the Office for National Statistics proposals to create what's described as a sustainable and future proof system for producing essential statistics on the population.

Joining me to unpack all that and explain how you can get involved in the consultation process is Jen Woolford, Director of population statistics here at the ONS. And we're joined once again by Pete Benton, Deputy National Statistician.

Pete in a previous episode, you described how the once in a decade census has been the bedrock of our population statistics for a very long time, but now it looks like some pretty fundamental change could be on the way? PETE BENTON Well, that's the question. What's the future hold? We've been doing a census for over 200 years now once a decade, and it paints a beautiful, rich picture of our population that's fundamental to planning all of our services that we use: health care, education, transport, they all depend on the number and type of people living in a given area. But the question is, can we get more detail from other data sources every year, and might that mean that we don't need a census in 2031? Because we've got enough and that's the question that we are now talking about. MF Okay, so before we go into the detail of how we might achieve that, then paint a picture for our listeners. When we talk about population statistics, what are they exactly? And why are they so important and to whom? PB Well in between a census, we estimate the total population, by age and by sex and we do it nationally and we do it for local authorities. We estimate migration, how many people have moved into the country and how many people have moved out and also how people move around the country because that affects the population at any given area. And of course, we also do surveys that give us top level national level statistics about all kinds of things whether it's the labour market, or our health, things that the census asks and gives us detailed information for small areas, surveys, kind of paint a top level picture in between times. MF So to date, how have we gone about getting those numbers, and how good has that information been? PB So the census gives us the baseline once every 10 years. And we take that and we add births, we subtract deaths, we make an estimate of international migration. And we use that to adjust the data and we make an estimate of migration around the country, and that gives us those population estimates and those migration statistics. MF So to do that you need, or you’d have had to have drawn on something like the census, that universal survey of the whole population. PB That's right. The census is the benchmark by which we reset the system once a decade. But of course, after nine years, that information is getting more out of date and we do a census again, 10 years on to reset those statistics. And again, give us that rich picture. The question we're looking at now is how much can we get in between times? And how much do we then still need all the detail that a census would give us once a decade? MF So Jen, the world has moved on in those decades since the census in its present form has been going. You would think there's an opportunity out there to transform how we go about counting the nation. Give us the background to that. JEN WOOLFORD So we've been looking over decades to bring more and more data together to improve our population statistics. So Pete talked about how we look at the movement of people between censuses both in and out of the country and between different areas. And for some time now, we've been using what we call administrative data to understand those movements in the population. But now we have access to lots more data than we have in the past, and it gives us lots of opportunities to change how we're producing population statistics. So back in 2014, government first set out its ambition for us to build a population and migration Statistics System with administrative data at its heart. In 2018, we published a white paper, which set out our plans for a digital first census in 2021. But also that we should be making a recommendation to government about what the future of Population Statistics looks like, and that that recommendation should be based on a public consultation. And that's the consultation that we are going to be launching at the end of June. MF The challenge therefore, is to come up with something as least as good if not, preferably better, but without using a census. JW Absolutely. And people's needs are changing. So whatever we do has to respond to whatever the user needs are of the day. So in the past, where maybe populations didn't change so much at a local level so quickly, then having a census once a decade that gave you that detail, that detail would still be quite relevant 10 years later. But the population is changing so rapidly now that that decade old data can quite quickly become out of date. And an example of where this could be a problem for us and for policymakers is if we look at the COVID pandemic. During the pandemic, we saw really localised outbreaks of COVID infections, and we really wanted to understand what was going on in those areas and what the characteristics of people in those areas was to try and understand what might be leading to those outbreaks. But we didn't have census data, the 2021 census data then, we were having to go back to what those areas look like in 2011. So by transforming what we do, and having more up to date information about those local populations, it would have given us a much better idea of what might have been driving those local outbreaks. MF And there was another example perhaps during the pandemic when the government was trying to work out what proportion of the population had been vaccinated at local level relying on population statistics that because they were backed up by the census was subject to quite significant margins of error. JW That's right. So if you want to know what proportion of people in an area have been vaccinated, you need to know how many people are in that area in the first place. And if you're looking at a vaccination rate that's really high say kind of 90% that 10% is what's important, the 10% that aren't vaccinated. Now, you might only have a 5% error in your population estimates. But that could mean that you're thinking you've got 15% of the population to look at rather than the 10%. MF Pete, we've heard this term admin data (administrative data) already. And in that we're talking about all the information that gets collected whenever someone engages with public services, tax bills, benefits, going to the dentist, that kind of thing. Now, presumably that information has been collected for quite some time. So why is it only in the last few years that we're really starting to see and begin to use the potential of that data? PETE BENTON It takes time to develop the methods for doing it. So we've put a lot of effort into understanding the data sources and understanding the quality of the statistics that result so that we can be clear what we can and can't do, and that we can show that to the people that use the data to make decisions in order to understand the quality of what they're getting and give us their views of that. MF Can you think of some examples of administrative data as already being used effectively in official statistics, the sort of things that the ONS produces. PB Well we've always used them actually, when we produce our population statistics. We estimate the local population using the number of people registered with a GP and how that changes over time. So it’s not new, it's just that we're expanding what we might be able to do here to try and get so much greater benefit every year, to improve decision making every year for all of our public service planning. MF And the opportunity, as Jen has already suggested, to link that data to understand how different groups, down to really quite small groups and local level and by different characteristics, are being affected by certain issues. PB That's right. Different datasets tell us different things. So there are datasets that tell us about educational achievement and there are datasets that tell us about household income, for example. And by bringing those together, we can understand the implications of education per outcomes of household earnings so we can really start to tie together the kind of public services that we get and the outcomes that we get as households. MF Now the possibilities of all this, of course, of being able to bring all this data into one place is a very exciting one from an analytical point of view, but from the point of view of the public and individual citizens at the same time, you could see why some people might be concerned about this, both from an ethical and a secure point of view. PB Well, when you think about it, this is nothing new for ONS. We've been doing a census for over 200 years and we keep those data safe we always have done, and we also do surveys every year of households on very sensitive topics. Some of them are people's experiences of crime or their health for example, and we do surveys of businesses to understand the economy and produce our statistics about GDP and inflation. Those data are all sensitive, and we keep them all very securely. So in one sense, there's nothing new here. We are good at this. We know how to keep data secure. It's all anonymized. So there is never anything published that identifies an individual and even within ONS, the analysts only get to see anonymous data. MF And very important to state, is it not, that it's not a question of building up pictures of individuals. It's always from a statistical point of view. It's the numbers we're interested in and not the people. PB Absolutely! We don't care about Peter Benton or Miles Fletcher, we care about the picture it paints of the nation. It's the statistics that come from it. And we are absolutely strict about confidentiality. MF Jen, other countries of course are wrestling with this as well and adopting and trying new kinds of systems. What's been the experience internationally? JEN WOOLFORD So you're right, lots of countries are looking at new and innovative ways to create the population statistics bringing lots of different sources together. We all operate in slightly different contexts. So in Scandinavia, for example, they've been producing population statistics like this for a long time. But those are countries that have population registers, which means their context is very different from ours. And to be absolutely clear here, we're not looking at building a Population Register. We're looking at creating statistics from bringing together different data sources. And there are a number of countries who are in the same position as us. So for example, Australia and New Zealand, and they are looking to try and develop similar systems for producing population statistics as we are and we're working very closely with those countries to share our learning and to share the methods as we're developing them so that we're all learning from each other. MF So talking about the potential of these new data sources, including all the administrative data, can you give us some examples of what we're not doing that we might be able to do much better in future? JW There are a number of advantages and improvements we can make for greater use of data. Firstly, in the existing system, we use the census to benchmark our population estimates. So in between censuses, we estimate population change with births and deaths and migration, but we tend to get a bit of a drift in those population estimates. So we use the census then to benchmark it and bring those estimates back in line. With this new system, we're looking at not just estimating the change but also estimating the number of people at a point in time, so that hopefully will reduce that drift that we get in population estimates and mean that over the 10 year period, our estimates are more accurate. The other thing that can happen between censuses is you can get quite a lot of change in local areas and the data we have doesn't reflect that change, because it's based on the previous census. So an example here could be that the conflict in Ukraine has led to a number of Ukrainian refugees moving to England and Wales since we conducted the census. So in some areas, the makeup of the population there will have changed significantly since we conducted the census. And in our existing system, we wouldn't be able to pick that up. With our new system, we'd be able to pick up that localised population change much more quickly than we can at the moment. MF And presumably that would be of enormous benefit for local authorities, where everyone would be trying to provide services down to local level, because you've got a much more up to date picture of how many people are there, and we saw recently when the census results were published, some local authority areas have experienced big changes in population. JW Absolutely. The other thing to be aware of with the census is that it was conducted during the pandemic and it was conducted during a period of lockdown. What we saw was that people moved out of some of the metropolitan areas during that period of lockdown, back to whether that's the kind of parental homes for students or for young members of the workforce. So the populations in those metropolitan areas will have changed quite rapidly as the country opens back up and as people move back into those metropolitan centres. The approach that we're taking now should be able to pick up that change much more quickly, not just the numbers of people, but also the characteristics of people who are moving within the UK. MF And how does this benefit individual citizens? What's this going to mean for the public generally? JW So better data means better decisions. It means that better planning can be made for things like school places, better planning for public transport, where to put hospitals, where to put sports centres. All of these decisions are based on our data about the population and by having better data, you'll have better decisions. MF And you’ll be able to target services and be able to target spending as well on a much more short term basis, rather than having to make decisions coming along into the future when circumstances could be changing. JW Absolutely. Or the decisions might still be long term, but you'll be able to monitor the impact that those decisions are having much more closely than you can at the moment. MF So Jen, is there anything we won't be able to get from such a system? And we've heard some people suggest, for example, that we wouldn't be able to get that very small level data, the street level data that's so useful from a census, and survey purists point, of the census as a great way of capturing social history. JW We're always faced with trade offs when we make decisions about things like our methods, or anything in life, and there are likely to be trade offs here. What we've done to date is we've done lots of research that shows that there's bags of potential here with what we can do with administrative data and the understanding of the population we can get from administrative data. There are still outstanding questions for us. So there are some characteristics, for example, people who provide unpaid care, that isn't available from administrative data and we still need to work out how we will provide that level of data. The census gives such a wealth of information about things like ethnicity where we get down to really granular classifications of ethnicity, it may not be possible to do that with administrative data. However, on the flip side, we can produce statistics that we didn't get from the census using administrative data. So on the 2021 census, we didn't collect information about income. But we've published research that shows that we can get down to small area estimates of household income using a combination of administrative data. We've also published research which shows that we can produce the kind of variables that we do get from the census. So we've published research on ethnic group and also on housing stock, types of housing, and we've also managed to get to linking different admin data together so that we can look at income by ethnic group, and housing type by ethnic group. So producing what we call multivariate statistics through linked administrative data. We still have a programme of research to really understand how far we can replicate what we get out of the census. But the consultation that we're about to launch is really about understanding whether what we can demonstrate and deliver with administrative data answers user needs. And if it doesn't answer some of our user needs, what are those needs, and so we can then plan our future research to make sure we're focused on the right things. MF And of course, it's genealogists - people who love to trace family trees - who find the census data so valuable. JW Absolutely. And in the existing system census data is archived for 100 years and then made available to genealogists and others to really explore their family history. In the new system we have a wealth of data that we could be using to understand the population and we need to work with genealogists to understand exactly what it is that would be useful for us to archive for future posterity. So although that's not the focus of the consultation, genealogists are very welcome to respond to the consultation and let us know more about their needs, or we'll have future conversations to make sure that we're clear on what the need is here and how we can best answer it. MF And that's what the consultation is, to a large extent, all about.

JW

Absolutely.

MF

And it's important to understand that these proposals haven't just been whipped out of thin air, a considerable amount of work has already gone on getting us to this point in time hasn't it. Can you talk through some of the research that's already happened and some of the evidence that has been provided to suggest that a new and transformed system might well be the way forward? JW Yes, this has been a long programme of work where we have focused on two different types of research. One is around improving our estimates of the population and being able to get to small area population estimates more frequently than we can at the moment. And the other is around the characteristics of the population. So what can we say about ethnicity or employment down to local areas. On the first of those, we've done a lot of work talking to local authorities about the estimates that we've produced and their understanding of our outputs and whether they match with what they see on the ground. We have compared what we get through administrative data to the figures that we got from the 2021 census. So lots of work comparing the outputs and talking to our users about how credible those outputs are. We're also looking at how can we improve our estimates of migration, in particular international migration, and we've been working very closely with the Home Office and the data that they hold to understand more about the flows of people in and out of the country and the reasons for those flows. So people coming as international students, people coming to work, people coming along humanitarian routes, and we've built already lots of improvements into our migration statistics using administrative data and we've got lots of plans going forward for even more improvements that we can deliver there. We also have an expert panel, the methodological assurance review panel, who quality assure our methods. So these are people who are real experts in statistics and methodology, who have looked at the detail of the methods that we're using to produce those outputs and check that those are sensible and the best methods that we could be using. MF So to sum up then Jen, how far ultimately could this new system take us?

JW Well, the sky's the limit, really. As more and more data become available, there's more and more we can do, as our methods improve. As our computing power improves, there's more and more we can do to really understand the population, its characteristics, how it moves around. So this is going to be an ongoing programme of work for years to come. MF So Pete, tell us then about the specifics of the consultation. Who is it for and what do we hope to get out of it?

PETE BENTON Well, it's for anybody who would like to respond. We in particular, want to hear from people who use the statistics to get their view on the balance between all that detail that the census gives us once a decade compared with the frequency of having more information every year, and we want to understand people's perspectives on those trade offs, but anybody is welcome to respond to it. And of course, this is just the continuation of a conversation that we've been having for years. We're continually talking to the big stakeholders, the big users of our statistics across government, in local government, in the commercial sector to understand their needs for statistics. So this is a culmination of a conversation that's been going on for years. MF Okay, so when does the consultation start? And how exactly do people go about taking part?

PB

Well, it'll be an online consultation. It'll start in June and it will end in October. MF Okay. So the consultation completes in the autumn. Big question - what happens then? PB So we will take a good look at all those responses we will understand what people have told us and then 12 weeks later, we will put out our response to that consultation summarising what we've heard. Following this, the National Statistician will make recommendations to government based on all of ONS’ research and the findings of the consultation to put administrative data at the core of a transformed population and social statistics system, and that recommendation will also consider the future of the census arrangements. MF

So there you have it, a one in a million opportunity – or more pedantically, one in 59.6 million, given that’s the accurate population of England and Wales according to the last census - to share your views on an incredibly important piece of work.

Consultation opens on June 29th and runs through to the end of October. If you'd like to find out more about it and all of our transformation plans for population and migration statistics, you can do so by visiting the ONS website: www.ons.gov.uk Or you can attend one of the free in person and online consultation events that the ONS has organised in July, details for which you can find on this episode's podcast page, as well as online through our social media channels, and the ONS website.

Thanks to Jen Woolford and Pete Benton for taking us through everything today. And thanks as always to you for listening.

You can subscribe to new episodes of this podcast on Spotify, Apple podcasts and all the other major platforms. You can also get more information by following the @ONSfocus feed on Twitter.

I’m Miles Fletcher and from myself, and our producer Steve Milne, thanks for listening.

ENDS