I thought it was you who appealed straight away to ''religion in numbers''.
My interest and my engagement in this thread has largely been about explain
why the numbers change - something you seem unable, or unwilling to grasp. In your eyes religiosity going up and down seems to be akin to this years' fad, next year we will see something different. When you understand
why the numbers are changing in the UK (and many other similar countries) then you will understand that the effect is locked in for the next 40 years, probably more. The one caveat being migration of people into the UK, but this isn't really a change in religiosity, merely moving religious or non religious people from one place to another.
I held off talking about China until quite a way into the conversation and then only to show that decline in christianity has been preceded by a rise in Christianity.
While there may have been changes in active participation in christianity in the UK over the past centuries you'd have to go a very, very long way back for an increase in the proportion of people in the UK who believed in christianity - probably 1000 years.
Conversion is a recognise term in religion. Active seems like a word from social science.
Actually conversion is an extremely hard thing to assess except by proxy as it really reflects a change in internal belief. Conversion is typically assessed by one of a number of aspects of religiosity, typically self-identified affiliation, importance and active involvement in christianity. Active involvement (i.e. activity) is far better recognised and easier to assess - you can actually measure the numbers of people attending worship, you cannot easily assess conversion as you get people like you and AM who claim conversion when in reality this is nothing of the sort as your upbringing involved heavy dollops of Christianity which you retained as adults.
Voas seems to have a narrow study period, seems to have the opposite of survivorship bias, and restricts his geopolitical area of study.
Actually his studies have sufficient understanding and length of data (you need a cohort approach to understand what is going on) to be able to accurately tell the story of the past 100 years and predict what will happen until the cohort of current teenagers have largely died, by about 2080. That sounds pretty long range to me.
I am one of those christians who believe it is true for everyone.
But that is merely a belief, a subjective opinion not backed up by evidence - hence it cannot be considered to be an objective truth, at best it is a subjective truth.