I can't be bothered searching for statistical analyses, so I shall rely on anecdotal evidence. A favourite quote of mine (which I just invented) is "anecdotes beat statistics." This would seem to be true in that word-of-mouth travels faster than those facilitating the NZ Census etcetera.
Let us accept that the Church (say, for example my home-by-choice of the Anglican Church) has declined significantly in the West, including NZ. Apparently this has "implications, no?" I write this in response to a request; let me know how I fare.
Let us break it down.
Maybe if the Church is God's people on earth it should always be visibly growing. This is not a biblical claim and I don't see much reason to believe it, but it would not be a problem if it happened! Well, a problem for some perhaps; like those engaged in trafficking children, warmongers, those who exploit the environment, those who rely on secular humanism (yet also God) for selling their blasphemous books and those who like their sins to be acceptable. Anyway, a claim I do see in the good book is that the Church shall always exist. No sign of it dying completely yet, so all good so far. Perhaps in the next few decades, the Church will though die in the West and the primitives in other countries shall gratefully inbibe our medicine of hopeful hopelessness as well. Perhaps.
The signs aren't good so long as passionate evangelical and charismatic Christianity continues to explode (in a good way) in places like Nigeria; while the Chinese middle classes and academics convert to the point where Jesus is bigger than The Party; and signs-and-wonders show up in South America such that the God of Christianity is given the glory.
But am I not just distracting you from where the real wisdom is to be found - secular New Zealand and perhaps Europe (the States; economic and scientific superpower, is an aberration clearly not worthy of mention)? Yes and no. In Europe (& North Africa and S-E Asia) Islam is doing pretty well, partially through high birth rates (as well as, in a different place, conversions in US prisons; but perhaps that particular phenomenon has decreased.) OK, sarcastic/ironic asides aside, obviously I'm still just trying to hide that my Church/religion is dying and isn't worthy of your time (catch my little rhyme?) Well, the pentecostals and non-denominational evangelicals are actually doing pretty well numerically (e.g. Life, Arise, Harbourside, GCC, WCCC.) In the Anglican Church in Auckland, a number of my friends' churches aren't doin too bad either IMHO, most clearly St Pauls, having increased about 10fold (or more) in 6-ish years to a roll of ~1000. We do have issues with theological liberalism, which can kill churches. The Presbyterians at least, I have heard, have managed to turn around to a significant extent wrt this and there is hope yet! More obviously problematic are our demographics - apparently the average age at churches in the UK (I assume the CofE) is 61 and I guess we're in a similar boat. There is a baby boomer bubble in the population-at-large and so as this ages and deceases, a bit of reduction is to be expected in churches which aren't able to engage more recently formed generations.
There is also a general decline of the prominence of the established churches in society; I suppose the growth of the state in providing welfare may have something to do with it as the instigator of this post suggested, but in recent years it seems more attributable to growth in immigrant populations and consequently, adherence to other faiths. Christianity also loses many young people, often in their 20s - sometimes they come back to a church when they have children. Clearly Christianity is not inherited like the wrinkly trait in peas (note: actually, since the trait is recessive (and most churchgoers are wrinkly) maybe there are some similarities!) A cultural shift away from taking Jesus seriously is truly concerning for someone who cares about people - but is not necessarily any kind of defeater for religious belief. The Church has continued to see many conversions in recent years. I can think of a couple of handfuls of friends and associated hoi polloi who've left the non-faith or luke-warmish-agnosticism of their parents; long may it continue! Even in the small youth network of the Anglican Church, perhaps even more so than elsewhere, I have met a few such critters. Academics too retain, accept, or return to faith; even on these skeptical shores. As our culture's media and other structures are secularised (not sense of becoming completely atheistic, just less Church-friendly), Christianity polarises as it did not so much in the 50s. Nominal adherence drops (surprise!), but does the number who actually believe in the salvific death and resurrection of Jesus and live accordingly? Atm for me, that's an open question. It will be affected by; amongst others; you, the readers of this blog!
The Church is an unpopular minority force in our culture, but it continues to impact lives for good. Good does in fact exist, as God does - and His people, for better or worse, remain the Church.