Many Sikhs around the world this week celebrate the birth of Guru Nanak, founder of Sikhism, India’s fourth-largest religion.

Most of the world’s Sikhs live in the Indian state of Punjab, the region where Sikhism began. There were around 21 million Sikhs in India as of the country’s 2011 census, accounting for 1.7% of the population.

Observant Sikhs differentiate themselves in several ways, including keeping their hair uncut, according to our 2019-2020 survey of India. In our survey, 76% of Sikh men and women in India said they keep their hair long and 67% said it is very important to them that children in their families also keep their hair long. We also found that 37% of Indian Sikhs read or listen to recitations of the Guru Granth Sahib (the Sikh holy book) daily, and that 94% of Indian Sikhs consider this book the word of God.