Is Christianity growing or shrinking?

Between 2010 and 2020 the number of Christians rose by 122 million, to 2.3 billion. That is 6 per cent, against 15 per cent for everyone else, so the Christian share of the world fell 1.8 points, to 28.8 per cent. Pew names disaffiliation as the main driver of that fall: people raised Christian who now say they have no religion.

The projections, which still run forward from a 2010 baseline, have Christians growing by about 34 per cent between 2015 and 2060 and Muslims by about 70, which brings the two close to parity: roughly 3.1 billion Christians and 3.0 billion Muslims, about 32 and 31 per cent of the world.

Christianity is not shrinking in absolute numbers. It is losing share, and it is growing more slowly than the fastest-growing alternative. Those are three different statements.

It has already happened once. Sub-Saharan Africa passed Europe during the 2010s as the region holding the most Christians: 31 per cent of them by 2020, up six points in a decade, against 22 per cent in Europe. The European count fell 9 per cent over those ten years, to 505 million, and the North American count 11 per cent, to 238 million. The projections take the African share to 42 per cent by 2060.

In 1910 about two thirds of the world’s Christians lived in Europe. The institutions, the arguments and the music follow the people.

In 41 countries the Christian share of the population moved by at least five points between 2010 and 2020, and in all but Mozambique it moved down: Australia by twenty points, Chile by eighteen, Uruguay by sixteen, the United States and Canada by fourteen each. Pew attributes most of that to disaffiliation, adults raised Christian who now report no religion. The age gap runs the same way, though it is narrower than it is usually made to sound: adults under forty are less likely than their elders to claim any affiliation in 41 countries of 106 and more likely in two, and less likely to pray daily in 71 of 105.

The falls are scattered across every region, but many are in Europe and in other Western or English-speaking countries, where Christian majorities have been shrinking for decades. Seen from there, a regional pattern is easy to mistake for a global one.

A projection of this kind runs current fertility, mortality, migration and rates of switching forward. It is arithmetic about trends, not prophecy.

The input it handles worst is the one that moves fastest. Switching was modelled for 70 countries, holding 43 per cent of the world’s people, and the two most populous left out are China and India. Pew says what follows: if China moves toward affiliation, the global figure tilts with it, because most of the world’s unaffiliated live there. The 2060 run also still starts from a 2010 baseline that Pew has since revised, and nothing has yet replaced it.

The figures above count self-identification. A census answer, a baptismal register and a Sunday attendance count produce three different populations. In the United Kingdom, Pew found 55 per cent of adults calling themselves Christian while going to church a few times a year at most, against 18 per cent going monthly or more.

Traditions differ on which of those is the real number, and they are not being disingenuous about it. A church that baptises infants and a church that baptises believers on their own profession of faith are measuring different things because they mean different things.

A familiar theory holds that modernity dissolves religion, and the last century ran that experiment in several places at once with results that do not agree. Western Europe secularised, the United States did not on the same schedule, and the one region where Christianity is still gaining share, narrowly, is the one with the highest fertility. Pew finds affiliation lower where the Human Development Index is higher, which is a correlation across countries, not a schedule each of them has to keep.

Whether the European pattern is the future arriving early or a regional peculiarity is genuinely open, and a confident answer either way is usually a statement about where the speaker lives.

A count of adherents says nothing about whether the thing adhered to is true, in either direction. A shrinking religion is not thereby refuted and a growing one is not thereby confirmed.

That is obvious when stated and routinely ignored in practice, in both directions, usually by whichever side the current trend suits.