Measuring religiosity is a controversial business these days.

Consider the kerfuffle around the Census religion question (results yet to be reported). Should such a question be asked at all? What do you do with vexatious answers (i.e., the growing number of Jedi)? Could it really be that 71.6% of the population is Christian?

This is a problem which has two parts. The first is the many vested interests, real and imagined, in religious statistics. The British Humanist Association initially wanted to change the question in last year's Census on the basis that the 2001 result created the impression of a more religious country than was really the case. They also claimed that the results had been used as an ipso facto defence of all sorts of faith-friendly policy positions. When they failed to get the question changed, they launched a public campaign to encourage people to jump into the no-religion category. It will be to their credit, and our surprise, if they do not use a high result for the no religion category from the 2011 Census as an ipso facto argument for secularism.

All this isn’t helped by the second part of the problem, which is a lack of clarity around the nature of ‘religion’, ‘having a religion’ or ‘being religious’. At different times, and by different people, these things are taken to denote what people think or believe and at others what they do. In practice, it’s safer to think in terms of a more modest third option, which is that measures of religiosity are simply measures of how people are prepared to identify themselves – and to move from there.

The census (whether the figures are low or high) measures exactly that - loose affiliation. It doesn’t measure practice. It doesn’t measure knowledge. It doesn’t measure belief. It doesn’t mean the churches are full to bursting. It doesn’t mean that this is a Christian country. It can't short-circuit public debate on any given policy issue. When affiliation statistics look wildly different to statistics on practice or belief, they’re not invalidating each other – they're just telling us that in the UK more people affiliate with a faith than practice it. Nonetheless, knowing who is willing to affiliate, even if they do not believe or practice, is information worth knowing – see Nick Spencer’s article here. But you do have to probe further to find out the significance of a statistic like that.

So rather than having less data, or data that focuses on the harder measures of belief and practice, our own argument has been that we should let all the flowers bloom but then encourage people to be responsible in interpreting and using the results. Think of it like measuring someone for a suit. There are all sorts of things of information that you might want and need: circumference of chest and waist, length of inside leg, breadth of shoulders and so on. It's better to have more measurements rather than less, but you better know what each measurement is a measurement of. If you don’t, then you’ll end up with a suit that doesn't fit.

In this vein, it’s important that people interpret the latest WIN-Gallup Index of Religiosity and Atheism (a repeat of a 2005 survey) carefully. Read superficially, it seems like a revival in the fortunes of the global secularisation thesis. The thinking would be along the following lines: atheism, globally, is 3% up and religion is 9% down. The poor and uneducated tend to be more religious than rich university graduates. As people become wealthier and more educated (and so more in touch with how the world really works) the less religious they will be. This is natural and desireable bi-product of progress.

If its sounds like a just-so story, then that's because it probably is. There are changes in this poll that can’t really be accounted for in that way and certainly can't be taken as evidence for the arguments set out above. A 21% drop in religiosity in France and Switzerland in seven years? What changed? Certainly not the slow and steady march of secular modernity. Similarly, 47% of the Chinese population of 1.4 billion people is atheist. For any number of reasons we should be extremely cautious about that figure, but we also don’t know which way it's heading (Gallup didn’t include China in the survey in 2005). In building a reasonable picture of global religious trends, little details like that are hugely important.

The WIN-Gallup poll’s biggest problem, however, is that it falls foul of the second problem of religious statistics, which is to say that it is wilfully unclear about what aspect of religiosity it measures. The question in the poll is clear that it’s not so much about practice ("regardless of whether you attend a place of worship or not, do you consider yourself to be…"). But it assumes therein that it’s asking people whether they hold religious beliefs – we know that because the alternative - atheism - is first and foremost a matter of belief. Unfortunately, things are much more complicated than that: some people might refuse the religion category not on the grounds of unbelief but, on the contrary, because of the strength of their belief (the 'Christianity is not a religion' trope is influential within western Protestantism). There will the plenty in the religious and not religious categories who have varying levels of belief and varying levels of practice which are hidden underneath these catch all categories.

Human beings are very good at developing stories which enable us to take account of complex information. Those stories can help us build a picture of the world when the facts refuse to speak for themselves. But when stories are used to ignore, rather than to take account of, complexity then they do not help but hinder. Interpreting this data through the lense of the secularisation thesis does exactly that. 

Paul Bickley