On Monday, the Office for National Statistics released its first wave of findings from the 2011 census for England and Wales (Scotland, you will have to wait until later in the year).

The census data shows how rapidly the population of England and Wales is aging. Why is this important for researchers?

Have a look at the age distribution for England Wales:

The chart shows a long ‘tail’ of people aged 70 and over, so much so that they form 12% of the population. What this does is to skew upwards any averages we want to make when age is included in our analysis. For example, the average age of people in England and Wales is 39.3 years. Yet when we exclude people aged 70 and over we get a lower age of 34.5, which is much more representative of the bulk of the population.

To see how this can affect our research, let’s look at the proportion of internet users in the UK who are likely to discuss online a programme they are watching on TV. Across all internet users, it’s 25%. Yet when we look at age groups, this doesn’t look right.

If each of these segments had the same number of people in, the average would be 31%. The reason for this six point difference is that there is a long tail of people aged 55+ in the internet user population. Only 12% of these people discuss programmes online whilst watching TV, but because there are so many of them, they skew the average down by six percentage points.

What is the implication of this? That an aging population means we need to be much more careful when using averages, because they can conceal the behaviour or characteristics of the bulk of the population. When once we could use averages to create simple pictures of the population, often this will no longer be the case.