The “legacy data” folder in each data set contains questions that are no longer fielded in the relevant survey.
Data availability in GWI Core is often tied to specific introduction dates for each question, meaning some datasets start from the quarter in which a question was introduced. For accurate trend analysis, always verify when a question was added to the dataset.
Why do we remove questions?
We tend to remove questions for one of the following reasons:
The question is no longer deemed sufficiently relevant to today’s digital consumers and hence it’s replaced by a different question
There’s now a better or more comprehensive way to ask the question and hence it’s replaced by a newer question addressing the same topic more effectively
How should I use legacy data?
Once a question has been removed from one of our surveys, it's best to avoid using it in any analyses or audiences. That said, there are some occasions in which it can be useful to do so. If you plan to use legacy data, be mindful of the following:
If a question has been replaced by a newer version looking at the same topic, you should avoid trending the two on a like-for-like basis. Any wave-on-wave shifts are likely to be the result of changes in question format or wording rather than a reflection of a real world change.
When building audiences, you can’t combine current and legacy questions where there are no overlapping waves using AND.
When building audiences, you can combine current and legacy questions where there are no overlapping waves using OR. However, changes in question format or wording mean that the audience may be noticeably different in size from one wave to the next.
Before analyzing or trending data, always verify the timeframe of the available data by reviewing question notes. This ensures you avoid conflating changes in question wording or format with actual trends. Additionally, when using legacy data for related context, check if the older datasets align with newer questions. While they may provide useful historical context, discrepancies in definitions or formats could impact your analysis.
To verify the availability of data for a specific question, you can check the Question Notes in the GWI Core platform by clicking the 'i' icon next to the question. These notes detail the waves, locations, and introduction timelines for the question, helping you understand its data coverage.