Patrick Johnstone authored Operation World, "the definitive prayer guide to every nation." The resource has sold more than 2.5 million copies and is considered by many to be the most important missions resource in history. Johnstone, a former missionary, recently took on another writing project of equally impressive scope: The Future of the Global Church (IVP, 2012). The book includes data on global history, demographics, and religion.

What are some surprising developments in Christianity globally?

The 1990s was the greatest harvest into the kingdom of God that the world has ever seen. Part of this is due to trends in demographics. The places where Christian faith has flourished have also been the places with the greatest population growth. Evangelical Christians went through a wilderness period from the 1920s until the 1960s. But now evangelicals are a leading expression of Christianity. I recently spoke at an Anglican clergy conference and said, "Do you realize ...