1910 AD - ~35% of people in the world are Christians
And after a century of television, radio, airplanes, assembly line factories, xerox machines, internets, etc. (all of which gives richer western nations--ie. heavily Christian areas--a huge technology and resource advantage when carrying out missionary work)...
2010 AD - ~32% of people in the world are Christians
Clearly we're doomed.
I am too lazy (I am going to bed in 5 minutes) to put my critical thinking beret on. But my guess is that this number you are disconcerted about stems primarily from dates 1910 to 1920. The genocide of the Armenians and Greeks in Turkey. World
War I (with 4->10% loss in the population of France, Germany, and Serbia (especially). World War II which I am not going to look up the facts because it should be clear to you.