"Assessing rates of belief or disbelief among large populations is extremely difficult. Determining what percentage of a given society believes in God – or doesn’t -- is fraught with methodological difficulties, most importantly: 1) low response rates, 2) non-random samples, 3) adverse political or cultural climates, and 4) problematic cross-cultural terminology. A brief discussion of each is warranted before presenting an accumulation of statistics concerning rates and patterns of atheism worldwide.
According to Inglehart et al (2004), 31% of those in Norway do not believe in God. According to Bondeson (2003), 54% of Norwegians said that they did not believe in “a personal God.” According to Greeley (2003), 41% of Norwegians do not believe in God, although only 10% self-identify as “atheist.” According to Gustafsson and Pettersson (2002), 72% of Norwegians do not believe in a “personal God.” According to Froese (2001), 45% of Norwegians are either atheist or agnostic."
This chapter is forth-coming in the Cambridge Companion to Atheism, edited by Michael Martin, Cambridge University Press, 2005
A very thorough summary! Being Norwegian I took out the part about Norway as an example.