and that its presence works as an indicator of the actual degree of mestizaje present in a given population, having its lower frequency in Uruguay with 36%, followed by Argentina with an incidence 44%, Mexico with 50%-52%, 68% in Hispanic-Americans and 88% in highland Peruvians. A study performed in hospitals of Mexico City reported that, on average, 51.8% of Mexican newborns presented slate grey nevus, while it was absent on 48.2% of the analyzed babies. According to the Mexican Social Security Institute nationwide, around half of Mexican babies have the slate grey nevus. Central American indigenous children were subjected to racism due to their slate grey nevus but progressive circles began to make having the slate grey nevus popular after the late 1960s. Highland Peruvians have the slate grey nevus. Treatment As a congenital benign nevus, Mongolian spots do not require treatment and in most cases disappear before adolescence. No cases of malignant degeneration have been reported. Cultural terminology The slate grey nevus is referred to in the Japanese idiom shiri ga aoi (), meaning "to have a blue butt", which is a reference to immaturity or inexperience. In Mongolian language, it is known as "Хөх толбо". Korean mythology explains the nevus as a bruise formed when Samshin halmi or Samsin Halmoni (), a shaman spirit to whom people pray around childbirth, slapped the baby's behind to hasten the baby to quickly get out from the mother's womb. "Mongolian Mark", the middle third of the 2004–5 novel The Vegetarian, is named after the title character's nevus, which obsesses her brother-in-law. In Chinese, it is referred to as "青痕" (Pinyin: Qīng Hén; literally: blue mark). Among common folk it is said to be caused by the Buddhist goddess of childbirth Songzi Guanyin (Simplified Chinese: 送子观音; Pinyin: Sòng Zǐ Guān Yīn; literally: the goddess of baby sending) when she is slapping the baby's backside, telling it to be born. Others say it is because the baby does not want to leave the mother's womb, so Songzi Guanyin will kick it out, leaving the bruise. A small portion of people wrongfully believe it is caused when the doctor is slapping the baby's backside to make it cry. Scientifically, it is also referred to as "蒙古斑" (Pinyin: Měng Gǔ Bān; literally: mongolian spot) In Khmer, it is known as "khnau" (ខ្នៅ) which translates to 'Mongolian spot' as well as other skin conditions such as