Hard to get a good handle on facts, especially in a place like Indonesia, with its many, many islands, languages and peoples. However, let's think this through.
A high-side optimistic estimate would be one million conversions from Islam to Christianity per year. (Conversions don't all come from Muslims; they come from Animists and even from Chinese Communists in Indonesia, too.) The population of Indonesia is around 250 million, about 80% Muslim, 10% Christian, and 10% another including Hindu, Confucist and Animist. So, say 200 million Muslims. If one million convert from Muslim to Christian per year, that makes the annual conversion rate 0.5%.
Speaking carefully, five tenths of one percent is not what I would call massive.
(I am chastened when I think of a handful of people in my own family who have in practice exited Christianity. I would bet that many Freeper families know the sadness of seeing many -- well, use the term "backslidden" family members.)
I could well be wrong. I want to be wrong. I am open to the Holy Spirit's surprises.
There are many Muslims converting to Christianity in Indoneisa — which is a doubled-edge sword for the transformation of Indonesia.
Here’s another story on the phenomenon:
http://my.news.yahoo.com/christian-indonesia-big-threat-to-malaysia-says-muslim-052831228.html
Muslims are worried and they claim that TWO MILLION Muslims convert to Christianity in Indonesia every year — and here’s a YouTube video the Muslims made to counteract this trend:
Indonesia has the world’s largest Muslim population. A transformation here would be a huge defeat for Islam and a huge victory for Christianity.