It’s been three years since 2011 census data is available with the Government. Is three years’ time not long enough for any Government to make public; one of the most crucial part of the census? The religious demographics data shows religious populations by proportion. There are lots of theories around as to why this key data is not made public.
I don't have any insights into this, except that in looking at the 2011 Census questionnaire it appears to me that there are several items of information that have not yet been made public on the Census India website. It doesn't seem unusual that the second most populous country in the world would require a fair amount of time to process census data.
Until the census data are released, the best estimate of the Muslim population of India comes from Pew Research, which suggests that in 2010 Muslims accounted for 14.4 percent of India's population, an increase from 13.4 percent in 2001. Since these projections are based on demographics trends since 2001, it is very unlikely that the 2011 Census will be very different.
What is important to take away from the Pew report, however, is to remember that while the Middle East has the highest concentration of Muslims in terms of the percent of the population in a given region of the world, and while Indonesia is the most populous predominantly Muslim country in the world, India actually has the second highest number of Muslims of any country in the world--close behind Indonesia. When the Indian subcontinent was partitioned into India and Pakistan (which subsequently was divided into Pakistan and Bangladesh), many Muslims stayed behind. As a result, there are more Muslims in India than in either Pakistan or Bangladesh and the Indian subcontinent is the most populous region of the world in terms of Muslims. I don't personally see that as dangerous or alarming, but it is a demographic reality that is rarely discussed in the western world.