Why are the population figures different in profile and forecast.id?
One of the more challenging aspects of working in the demographic field is the multitude of different population figures we have to deal with. If it’s not a final figure, it’s probably preliminary, revised, recast, recalibrated – you name it – population figures released by statistical agencies and other organisations such as .id can be confusing. Luckily the demographers at .id are skilled in dealing with these changes and we like to make things seamless for our clients. Here’s a few reasons why you might find different population figures in our products.
It’s a Census figure
In Australia, the Census of Population and Housing is conducted every five years. There are two population counts that Census users need to be aware of – the enumerated population (where you are counted) and the usual residence population (where you normally live). They can be different because you may not be at home on Census night eg on holidays somewhere else in Australia, away for business. For example, the snowfields in NSW and Victoria have a high enumerated count at Census time as it’s held in August, the height of the ski season. The reverse is true in the coastal regions in Australia’s south and is typically shown through high dwelling vacancy rates because holiday homes tend not to be occupied on a Tuesday night in winter and therefore the enumerated count can be lower than the usual residence count.
Users of Census data should always be aware which figure they are using – enumerated or usual residence. One common mistake is to compare two different points in time using enumerated for one year and usual residence for the next. Yikes! This is like comparing the proverbial apples and pears. Profile.id has an option whereby you can choose which count you require, but note that usual residence data is only available back to 2001 as the ABS did not code this variable for small level geographies before this time.
It’s an ERP figure
The ERP stands for Estimated Resident Population. It is the official measure of Australia’s population produced by the ABS, and is released on a quarterly basis for States and Territories, and annually for smaller geographies such as LGAs. In profile.id, we publish the ERP count under the Post-Census updates menu – select the Population estimates option. Currently this has a time series showing data from 2003 to 2013, the latest year for which LGA estimates are available. More detailed data is available on the ABS website.
It is important to note that the ERP is subject to revision and that every five years the data is rebased and the annual data from the previous intercensal period is finalised. This means that when the 2014 ERPs are released, the 2013 is likely to change as it is currently a preliminary figure. Furthermore, after the 2016 Census, the ERP figures for 2012-2016 will be finalised based on the results of the 2016 Census and post-enumeration survey.
It’s a forecast figure
.id produces population and dwelling forecasts for over 120 councils across Australia. We have a program of continual updates for most of our clients and we are currently undertaking forecast reviews using the 2011 ERP as the base figure, with a forecast period of 25 years ie 2011-2036. Forecasts are progressively updated on the .id site as they are completed.
Forecast.id matches the ABS final ERP for 2011 only. Each subsequent year is a forecast figure based on our analysis of development patterns, building approvals and other data. As such, the forecast population figures for 2012 onwards may not match the ERP figure produced by the ABS. This can create confusion but it’s important to note that they are measuring two different things and the choice between which one should be used depends on what use you’re putting it to. For example, we recommend that clients who are looking at future servicing requirements use the forecast figures rather than trying to combine the two.
We are sometimes asked – why don’t you match the ERP and forecast figures for all past years? The answer is simple and I’ve alluded to it above – the ERP is subject to revision and is rebased every five years. For example, if we match the 2013 ERP for forecasts we are currently updating, then that figure will likely change in April 2015 when the 2014 ERP is released. We also believe that our in depth analysis of development trends and knowledge of place puts us in a good position to make an expert judgement about population change.
Visit our demographic resource centre to access free online community profiles (profile.id) and population forecasts (forecast.id) for your area.
Simone - Myth Buster
Simone has a rich background in human geography, demography and urban planning – a background that was useful in her previous roles in the Commonwealth and State Governments, and now as part of the forecast team at .id. From the Queensland coast to the southern suburbs of Perth, Simone produces population and dwelling forecasts that help local governments make informed decisions about future service and planning needs. She is a regular contributor to .id’s blog and has spoken at several conferences on how our cities and regions are changing. She is a big advocate of evidence-based planning and how Census and other data can inform this. Outside of work Simone is a keen traveller and photographer – interests that tie in well with her professional life and help her to understand “place”.
