A Plea for Better Mapping

As data from the 2011 census is now beginning to be released some interesting facts are emerging. One of the most recent being in relation to the distribution of second addresses both in terms of where they are and where the people who use them normally reside.

According to new figures released by the Office of National Statistics there are now more than one and a half million people with second addresses in England and Wales. The 2011 census records people who spend more than 30 days a year at a second address. At 23,000 Cornwall has the largest number of recorded second addresses. These are not necessarily holiday homes. They could be places were people stay when on business, student addresses or other temporary accommodation. Of the people who recorded second addresses only 11% said they were for holidays and 12% for work.

As with all data that has a geographic content it is not very long before people start to map the data. The BBC has put together an interactive map that shows side by side displays of where second addresses are used by people from outside the local authority area alongside a map showing where the people who have second addresses outside the local authority usually live.

I often have an issue with thematic maps such as these. Are they displaying the data in the most appropriate way? Maps can lie and it is easy for those who produce such maps to manipulate the data classes, the number of ranges, the colours and even the way the data has been represented to mislead whether intentionally or unintentionally.

Looking at the map on the left the largest local authority areas have the greatest number of second addresses – just as you might expect as these authority areas probably have the greater number of properties anyway. A clearer and more meaningful representation may have been to consider the proportion of second addresses in comparison to total number of addresses.

The map of holiday homes presents a truer representation of the data as far as I am concerned. Here values are depicted as a proportion with Gwynedd in Wales having the highest proportion of holiday homes closely followed by the rest of north and west Wales, areas of Cumbria, East Anglia and along the south coast.

The abundance of geographic data and the availability of mapping tools means there is a growing tendency to map data – a move that I am pleased to see and support. However, please can we think and be clear about what we are trying to represent. Maps can be a very powerful way of getting information across – as the saying goes “a picture is worth a thousand words”. But it needs to be a relevant picture and geographic data needs to be analysed and displayed in the right context.

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