Rates vary between different regions of the world, from as few as 1 in 300 to as many as 1 in 40, with an average of between 1 in 100 and 1 in 170 people.
Angkanya bervariasi di berbagai wilayah di dunia, mulai dari 1 dari 300 hingga 1 dari 40, dengan rata-rata antara 1 dari 100 dan 1 dari 170 orang.