I have spoken about this a lot before but up to now the only statistics i have had to link to are in estonian not a problem for me but hard to use for others..
Check this link out for an indication of how much religion (not just Christianity) is important to Estonians or rather how marginalised religion is in Estonia...
(Interestingly a survey of 1000 people is more representative the smaller the country considering the size of Estonia its a biiig sample)
