Since the early 20th century, with the rise of mass secular education and the diffusion of scientific knowledge through popular media, predictions of the deity's demise have fallen short, and in some cases—such as in that of the U.S.—religiosity has actually increased. This ratio is changing. According to a 2013 survey of 14,000 people in 13 nations (Germany, France, Sweden, Spain, Switzerland, Turkey, Israel, Canada, Brazil, India, South Korea, the U.K. and the U.S.) that was conducted by the German Bertelsmann Foundation for its Religion Monitor, there is both widespread approval for the separation of church and state, as well as a decline in religiosity over time and across generations.

In response to the statements “Only politicians who believe in God are suitable for public office” and “Leading religious figures should exercise an influence on government decisions,” even in über-religious America only 25 percent agreed with the former and 28 percent with the latter. All other countries reported lower figures (with Spain at or near the bottom at 8 and 13 percent and Germany in the middle at 10 and 21 percent, respectively). Moreover, most of the countries in the survey showed a declining trend in religiosity, especially among the youth. In Spain, for example, 85 percent of respondents older than 45 reported being moderately to very religious, but only 58 percent of those younger than 29 said they were. In Europe in general, only 30 to 50 percent said that religion is important in their own lives.

Why the decline? One factor is the dramatic spread of democracy around the globe over the past half a century. Most people surveyed agreed that democracy is a good form of government, with no differences across religious faiths. One of the features of a democracy is the disentanglement of the sacred from the secular because in religiously pluralistic countries no one can legitimately claim special status by faith membership. Democracies also have higher literacy rates and mass education that lead to a tolerance for the beliefs of others that, in turn, lowers the absolutism most religions in the past required, thus undermining the truth claims of any one religion over others.

A second factor is the opening up of economic borders, such as between member nations of the European Union, which replaces zero-sum religious tribalism with nonzero financial exchange. Free trade and the division of labor constitute the greatest generator of wealth in history, and according to the Religion Monitor report using the survey data, “socio-economic well-being generally results in a decline in the social significance of religion in society and a decrease in the numbers of people who base their life praxis on religious norms and rules.” Why? One of the social functions of religion is to help the poor, so as a country's impoverished declines (and, as in Sweden and other European countries, government social programs aid the poor), so, too, does religiosity. And because the middle classes of most countries are growing from the youth up, that could explain the report's assessment that “almost all the countries in the study … exhibit a decline in the centrality and significance of religion for daily life from one generation to another. As a general rule, the younger people are, the lower their religiosity.”

Nevertheless, the authors caution about drawing the Nietzschean conclusion that God is dead: “This does not mean that religiosity and religious behaviour have vanished or will vanish completely from people's lives: between 40% and 80% of European citizens exhibit at least a medium degree of religious belief according to the centrality index of religiosity.” Still, the trend is unmistakable in another statistic from the study. The percentage of people who said that they are “not religious or not very religious” is significant, and the figure for the U.S. (around 31 percent) matches that of other studies.

A 2012 Pew Research Center survey, for example, found that the fastest-growing religious cohort in America are the “nones” (those with no religious affiliation) at 20 percent (32 percent of adults younger than 30), broken down into atheists and agnostics at 6 percent and the unaffiliated at 14 percent. The raw numbers are staggering: with the U.S. adult population (age 18 and older) at 240 million, this figure translates into 48 million nones, or 14.4 million atheists/agnostics and 33.6 million unaffiliated. That's a powerful voting block.