In general, the more affluent the country, the fewer citizens report that they are ‘religious’.
Note that Kuwait and the USA are outliers, exceptions to that general rule.

James A. Haught wrote about this trend:
Since World War II, worship has dwindled starkly in Europe, Canada, Australia, Japan and other advanced democracies. In those busy places, only 5 or 10 percent of adults now attend church. Secular society scurries along heedlessly. …
… males outnumber females among the churchless. “The ratio of 60 males to 40 females is a remarkable result …
Is this trend good or bad?
Good, I’d say, overall.
Religion works for some. I respect their right to freedom of religions so long as it doesn’t impose on others.
And any trend for less religiosity should diminish the fervency of religious extremists. We would hope.
Thanks Warren.
related – What atheists are really concerned about