There are between 49 and 51 Muslim-majority countries in the world, according to estimates from 2010. The fluctuation is a result of the changing demographics in countries where Muslims comprise around 50 percent of the population.
For example, since 50.01 percent is a majority but 49.99 is not, a slight discrepancy in population estimates can result in a country not being counted as Muslim-majority. Population percentages are frequently estimates, and different organizations can produce slightly different estimates. According to Pew Research in 2010, Nigeria has a Muslim population of 47.9 percent. However, others consider Nigeria a Muslim-majority country. Additionally, the numbers can fluctuate because of population changes due to immigration, death and birth.