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Frequently Asked Questions |
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| There seem to be so many different types of data. Which one should I use? |
| How can I access and download data from the ONS website? |
| How can I find out which Ward or Output Area I need data for? Is there somewhere I can look these up? |
| Can I compare 2001 Census data with 1991 Census data? |
| How accurate is the 2001 Census? |
| Why are the numbers often different when I compare the same information in different Census tables? |
| Tables seem to refer to different segments of the population. Why is this and is it important? |
1 | There seem to be so many different types of data. Which one should I use? |
| That really depends on the type of data you require since the different Census outputs (e.g. Standard Tables and Key Statistics) provide different levels of detail, different types of information, and vary in the geographic areas for which data is available. To simplify things, we suggest you follow these guidelines:
If you just need general information on a topic for a specific area (e.g. the number of households in Mid Bedfordshire with two or more cars) go to Key Statistics.
If you require very detailed data (e.g. the number of females aged 60+ in the Black Caribbean ethnic group living in Bedford Borough who suffer from a limiting long-term illness) go to Standard Tables. However, since Standard Table data is only available for wards upwards, if you require detailed data for an Output Area, go to Census Area Statistics.
If you want an overall picture of an area (a parish, town, ward, district or the County) with a wide variety of summary data, go to Profiles. |
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2 | How can I access and download data from the ONS website? |
| There are several ways of accessing and downloading Census data, but we recommend use of the Nomis website which is operated by the University of Durham on behalf of the Office for National Statistics:
Go to the Nomis site.
In the Detailed Statistics box in the central column, click on Wizard query.
Choose 2001 Census – Standard Tables for detailed information at the Ward level or above, or 2001 Census – Census Area Statistics if you require more general information, or you want data at the Output Area Level.
Under Go To Next Step click on Cell.
Choose a table, using the list. Keyword Selection can be used to narrow the choices and assist you in selecting the appropriate table from the large number available.
To select the entire table click on Select All. If you just require part of the table, choose the desired cells.
Under Go To Next Step click on Geography.
Use the list to select the required administrative unit, from countries down to wards (Standard Tables) or Output Areas (Census Area Statistics) and then choose your areas. Note that for Districts, Wards and Output Areas there is also the option of a map-assisted selection system. Other options include a search facility using postcode or place name.
Under Go To Next Step click on Extract Data.
Choose your preferred download format (Excel or csv files, or just view in the browser) and options (e.g. column descriptions).
Click on Download Data.
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3 | How can I find out which Ward or Output Area I need data for? Is there somewhere I can look these up? |
| The Nomis site offers a search facility using postcodes or place names which is accessible under Geography (see FAQ 2 above). Under Current Step choose Search and then enter the postcode or place name. It is likely that multiple options will be offered from which you must choose the required area – if in doubt, the area can be viewed in map form by clicking on the map icon next to each of the options.
Nomis also offers a mapping facility that allows you to view and select Districts, Wards or Output Areas. Using the method in FAQ 2 above, under Geography choose Select Some for Wards or Output Areas and then click on turn maps on. There is a zoom facility to assist in identifying the area. To view any Ward or Output Area in detail just click on the map icon next to the Ward name or Output Area code (09UDGL0003 etc).
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4 | Can I compare 2001 Census data with 1991 Census data? |
| Any comparisons with 1991 data must be treated with great caution since there are many differences in definitions and methodology between the 2001 and 1991 censuses; for example, in 2001 residents were counted at their usual place of residence rather than where they happened to be staying on Census night, as in 1991. Also, in 2001 students were counted at their term-time address rather than 'home' address as in 1991.
Additionally, changes in geographic boundaries may mean that areas with the same name relate to very different boundaries and are not comparable. This is particularly important when comparing ward data since the boundaries of most wards in Bedfordshire changed between 1991 and 2001 censuses though the name of the ward may not have changed.
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5 | How accurate is the 2001 Census? |
| Most of the criticism about the accuracy of the 2001 Census has related to possible underestimates of population in inner-city areas. Since this is less of an issue in Bedfordshire, we can assume that the Census is largely accurate in terms of Bedfordshire's population numbers and characteristics.
At the same time, it must be recognised that 2001 Census forms were filled out on a self-completion basis, and while the ONS did apply an elaborate series of measures to eliminate obvious errors (e.g. someone aged 180) and to impute data for those households not returning the Census form, it had to assume that forms were generally completed accurately and honestly.
Even though the ONS repeatedly assured people that Census data on individuals or individual households would not be used for non-Census purposes or correlated against other data held by Government, it is likely that some returns did include deliberately false information. For example, if a household owned a car with no road tax licence, it is quite possible that the Census form would indicate that the household did not own a car.
Overall, however, the 2001 Census provides the most accurate and comprehensive picture of the local population that we have access to, albeit one that is only a snapshot of the population on Census day – 29 April 2001. |
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6 | Why are the numbers often different when I compare the same information in different Census tables? |
| To ensure that no information about individuals or individual households can be identified, disclosure control methods have been applied to Census data. One of these methods is small cell adjustment. This can result in the numbers in the same data cell differing between tables and, also, in differences between column or row totals (for example one table might show the population of South Bedfordshire at 112,613 and another at 112,635).
Users should be extremely cautious of tables consisting primarily of large quantities of very small values. To minimise the effect of small cell adjustment, it is recommended that you use data for the largest geographical level that meets your information or research needs. |
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7 | Tables seem to refer to different segments of the population. Why is this and is it important? |
| Though many Census tables refer to the entire population (All People) many others are there to provide data about particular sub-groups of the overall population – e.g. those people who are working, or those living in communal establishments. It is essential that you check who is, and is not, included in the table you are working with and that you only compare like-for-like tables.
For example, if you want to calculate average household size you must choose, for your numerator, a table that shows the number of people living in households (i.e. one that excludes people living in communal establishments) and divide that number by the number of households (denominator). Failure to ensure that numerators and denominators reflect the same population is the single most common mistake made in the interpretation and analysis of Census data. |
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Help |
If your question is not covered in the Frequently Asked Questions above or on the ONS FAQ site, or for any other general enquiries, please call:
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The Corporate Policy Group | ( 01234 228372 (Int x42372) |
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| or contact us via email |
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Updated 30th June 2010
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