In the next three and half decades, the demography of world religions will change considerably with significant global consequences — political, social and economic. The proportions of the various religions in the world population will remain largely the same or decline, except for Islam. In South Asia, especially India, where tensions between majority Hindu and minority Muslims are on the rise such demographic change risks bringing upheavals.
Worldwide Muslims have the highest fertility rate and the youngest average age, and their number is projected to increase from 1.6 billion in 2010 to 2.76 billion in 2050. For the first time in history, Muslims will nearly equal Christians, until now the world's largest religious group in size. The number of Christians in the United States, Europe and Australia will decline significantly because of a larger increase in the number of those who identify as "unaffiliated," perhaps denoting agnostic or atheist.
These changes will also have repercussions for relationships between Muslims and non-Muslims globally, especially in South Asia — exacerbating existing tensions or giving rise to new challenges for promoting harmonious inter-religious group relations.
The Muslim populations of all South Asian countries will record varying degrees of change. Afghanistan and Nepal's Muslim populations will more than double. Bangladesh will register the smallest increase, around 36 percent. The number of Muslims in the Islamic Republic of Pakistan and Sri Lanka will increase by 63 and 48 percent, respectively. The largest and most consequential change, however, will be in India, poised to become the most populous nation. Its Hindu population will increase by 35 percent from 1.03 billion in 2010 to 1.38 billion in 2050, but Indian Muslims will increase by 76 percent from 176 million to 310 million in the same period. This means that the largest increase in the Muslim population of South Asia will occur in India.
India will acquire a new global status in terms of religious composition of its population. With a population of 310 million Muslims, India will become the largest Muslim "country" in the world. While Hindus will remain a majority population at 77 percent, the proportion of Muslims will increase from 14 percent in 2011 to 18 percent in 2050. The population increase will present additional and more complex challenges for the nation's democratic political system grounded in its secular constitution that envisions justice, liberty, equality and fraternity for all Indian citizens — but is increasingly contested.