Human resources can be classified into three categories based on skill: unskilled, skilled, and highly skilled. A nation's human resources productivity depends on factors like health, literacy, technical skills, industrious nature, motivation, and technological and infrastructure development. A census is a periodic governmental count of a population. India has conducted the census every 10 years since 1872, with the last one held in 2011 and the next scheduled for 2021. Population can be defined as the number of people living in a well-defined area, and it is distributed unevenly around the world.