World population growth is one of the primary factors driving the development of missionary strategy. The annual growth rate of the world’s total population grew markedly during the 1900s, so that strategies developed today have to engage with a very different reality from any previous century.

The chart below lays out the world’s population from AD 30 through AD 2050.

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In AD 30, the world’s total population was estimated to be about 170 million – something like half the total population of the United States today, or a little less than the current population of India’s Uttar Pradesh. Global population totals remained at about this level through AD 1000.

Around 1100 AD, the world crossed the 300 million population line for the first time. It took another 500 years to cross the 500 million line. When William Carey was born, global population was estimated in the 600 millions; when he died in 1834, the first billion had been reached. Thereafter, population growth became increasingly rapid. By 1900, the world had more than 1.5 billion people. A century later, in 2000, it had 6 billion. In a single hundred years, the world added more than 6 times as many people as all those who had been born between the time of Christ and the year 1900. It is no wonder to me that people were talking about ‘The Population Bomb.’ 

Looking at this chart, I see two different kinds of ‘closure challenge’.

• The period from AD 30 to 1900 is a period of slow population growth, with widely dispersed populations–and in all those long centuries, the world was rarely more than 20% Christian.
• The period from AD 1900 to 2000 is a period of very rapid population growth, in which the world has sustained itself at the 33% Christian mark.

For most of the time up to 1900, the world hovered around the 14 to 15% Christian mark. Although I would resist broad generalizations, those centuries seem to indicate the challenge of ‘finishing the task’ has never been purely about the immensity of the numbers. We can say ‘no one can reach 7 billion people’–but it looks like we had trouble reaching 100 million, too?

There are limits to this analysis–the USA is reached today, for example–but it’s worth exploring why the world hasn’t been reached. These figures seem to say it’s not because there’s too many people.