Globally, religion is in decline in North America and Western Europe, but is growing in the rest of the world. Although the number of atheists, agnostics, and people not affiliated with organized religion continues to grow in Europe and the United States, their percentage of the world population is falling because of their comparatively low fertility rate (1.7). In general, the growth or decline of a given religion is due more to age and fertility rather than conversion. Besides the level of education and income, how religious a woman is determines how many children she will bear in her lifetime. For example, in the cities of the Middle East, women who supported Sharia law had a 50% fertility advantage over those who opposed it the most at the turn of the century. According to the World Religious Database, the proportion of the human population identifying with a religion increased from 81% in 1970 to 85% in 2000 and is predicted to rise to 87% in 2025. In addition, the Catholic Church has gained 12% additional followers between 2000 and 2010, mainly from Asia and Africa. In 2018, Muslims had a median age of 23, Hindus 26, Christians 30, Buddhists and the religiously unaffiliated 34, and Jews 36. For comparison, the median age of the global population was 28 in 2018. Overall, Christians have a fertility rate of 2.6, and Muslims 2.9. Islam is the world's fastest growing religion. Meanwhile, the expansion of secularism will slow in Europe as the twenty-first century progresses.