Consistency over time and between collections
Hi - I think it's mentioned in the consultation document, but all the discussions on what to add to/change about the census got me thinking about consistency. I've done some analysis over time using HES, and changes in questions makes analysis over time more difficult. It can also be quite tricky/time consuming to track down all the information on which questions changed and how they changed. A couple of examples are similar to past changes to the census: changes in the way ethnicity was recorded and changes in home ownership questions to include trusts.
I understand that sometimes the benefits from changing things will outweigh the costs - in the 2 examples given above it seems clear that the change was for the better. But, I just wanted to flag that careful consideration should be given to any changes that mean that variables are not comparable (or are less comparable) over time.
A related issue is comparability across collections- eg, making sure that where HES and census collect the same information that this is done in a consistent way where appropriate.