evidence: According to Pew Research, the most religious areas of the world are experiencing the fastest population growth because they have high fertility rates and relatively young populations. Niger, the country with the fastest growing population in the world (3.7% annually) and the highest fertility rate (6.8 children per woman), is expected to quadruple its population by 2070. At the same time, the vast majority of adults in Niger (86%) say religion is very important to their lives (as compared to 54% worldwide). On the other end of the spectrum is Japan, where only 10 percent of their shrinking population (-0.5% annually) consider themselves religious. Japan’s population is expected to drop by 28 percent over the next 50 years. [...] Among the major religious groups Pew studied, Muslims had the highest fertility rate in 2015-2020 (2.9). The median age among Muslims was 23 during that time period, with over a third (34%) in the youngest segment of the population (birth – age 14). This compares to a median age of 28 for the world population with 27 percent ages 0-14. [...] Fertility rates for Hindus (2.3) and Buddhists (1.6) have been lower than for Christians and Muslims worldwide. Completed family size for those unaffiliated with a religion has been considerably lower (1.6) than the world average.