In fact, according to a study published in 2013, there was a net outflow of Rohingya from Burma after 1950—and that was before the unprecedented exodus of the last three months. Moreover, Burma’s Muslim population has been stable at around 4 percent since the 1980s, according to the country’s own census.

The trope of Muslim overpopulation is reliably powerful anywhere in the world where there is a sizable Muslim immigrant or minority population, from India to Western Europe.

Hindu nationalists often fan anxiety about Muslim population growth; the proportion of Muslims in India grew about 0.8 percent between 2001 and 2011, to 14.2 percent. “If this remains the situation, one should forget about their existence in one’s own country by 2025,” said the leader of a major Hindu nationalist organization last year. But the fertility gap between Muslims and Hindus in India is narrowing fast, and the greatest birthrate disparities are between states, not religions: Hindu women in the very poor state of Bihar have about two more children each than Muslim women in more developed Andhra Pradesh.

Similar concerns echo across countries like France, Germany, the U.K., and the Netherlands. Although Muslims make up less than 10 percent of the total population in each of these countries, perceived overpopulation has been at the center of anti-immigration discourse. About 7.5 percent of France is Muslim, yet on average French people believe Muslims constitute about one in three people in the country. Although Muslim women in Western Europe do currently have more children than their non-Muslim counterparts, research shows that European Muslims’ fertility rate is also declining much faster, so their fertility rates will likely converge over time. (However, in this context, fertility isn’t the only issue; a wave of Muslim immigration over the past few years has reinforced some Europeans’ concerns about Muslim population growth.)

Why does the overpopulation myth persist worldwide, even though it’s typically demonstrably false (like in Burma) or nowhere near the epidemic that its proponents assert (like in Europe and India)? It’s true that the global Muslim population is growing, and fast. But it’s not growing at the same speed across regions. And the trope seems to have the most power not where Muslim populations are actually growing the fastest—like sub-Saharan Africa—but in places where they are culturally distinct minorities.

There’s nothing inherent in Islam to link it to higher fertility—in fact, it’s not a particularly natalist, or pro-birth, religion. Eight of the nine classic schools of Islamic law permit contraception. Many Muslim states, including Pakistan, have supported family planning. The growth of the global Muslim population was, according to a 2011 Pew Center report, due to both a “youth bulge”—an unusually high number of young Muslim people, which peaked around 2000— and a higher overall fertility rate for Muslim women as a group.