Everybody loves statistics about life expectancy and the ballooning number of centenarians, but is there a risk they could become too much of a good thing?

The Office for National Statistics, whose field this rightly is, seems to be locked in competition with the Department of Work and Pensions to produce a never-ending cycle of bulletins and analyses that say almost but not exactly the same thing. There’s a danger of confusion.

The latest in this barrage of age-related statistics came from ONS at the end of last month.Timed for Older People’s Day 2011 (an anniversary new to me, which took place on 1 October) the Statistical Bulletin includes the latest estimates of life expectancy and the very elderly. For example, there were estimated to be 12,640 people over 100 in the UK in 2010, five times more than in 1980. And the gap between life expectancy at birth for men and women is lower in the UK (4.1 years) than i n any other member of the EU. Interesting stuff.

On the same day, it released Population Estimates of the Very Elderly which are National Statistics. This is a brief document lacking much commentary. The Older People’s Day Bulletin supplies the commentary, but is not classified as National Statistics. It’s not clear that publishing outputs in this way meets the requirements laid down by the UK Statistics Authority and outlined in its Assessment Report 103, Population Estimates and Projections, that National Statistics should be accompanied by commentary. 

Users may feel slightly confused about what is new and what is not. The same applies to the analyses that flow from the DWP. In the past year it has mined this rich seam no less than four times, by my count. Using ONS data it has produced a series of press releases and ad hoc analyses that have a political as well as a statistical objective – to lodge in our minds the fact that there are going to be zillions of elderly folk about in the future, so we’d better sort out the pension issue soon if they’re not going to bankrupt us. At least, that’s my interpretation.

The most recent DWP report, dating from 4 August, was on the chances of living to 100 by year of birth. It accompanied a press release with a quote from Pensions Minister Steve Webb saying: “The dramatic speed at which life expectancy is changing means that we need to radically rethink our perceptions about our later lives. We simply can’t look at our grandparents' experience of retirement as a model for our own. We will live longer and will have to save more.”

The data came from ONS, on request. There’s no reason to suppose they’re wrong. But they lack much explanation, and they aren’t new. The analysis explains that cohort life expectancy tables were used, but doesn’t explain what that means, or whether the results it gets are a forecast or a projection. There are high levels of uncertainty when predicting how mortality will change in future, but the tables contain no indication of the range of possible estimates, which might give readers a chance to gauge how great this uncertainty is.

The release got lots of coverage, in The Times, The Sun, the Independent, The Daily Telegraph, the Daily Mail, and others. The Times splashed on it on page 1, under a headline designed to shock – “Welfare in chaos as thousands live to 100”. To The Times’s credit, it did attribute the figures to ONS. Many other papers gave credit to the DWP.

So while this is a good way of making Mr Webb’s political point, it may not be an ideal way of publishing statistical data. It gives the impression of hundreds of figures tumbling out in a random way designed to shock rather than to inform.