Many of the migrants from China in the 19th century came to work on the pepper and Uncaria gambir plantations, with 11,000 Chinese immigrants recorded in one year. Singapore became one of the entry and dispersal points for large number of Chinese and Indian migrants who came to work in the plantations and mines of the Straits Settlements, many of whom then settled in Singapore after their contract ended. By 1860, the total population had reached around 90,000, of these 50,000 were Chinese, and 2,445 Europeans and Eurasians. The first thorough census in Singapore was undertaken in 1871, and the people were grouped into 33 racial, ethnic or national categories, with Chinese forming the largest group at 57.6%. Censuses were then conducted at 10 year intervals afterwards. The 1881 census grouped the people into 6 main categories, and further subdivided into 47 sub-categories. The 6 broad groups were given as Europeans, Eurasians, Malays, Chinese, Indians and Others in 1921. The Malays group includes other natives of the Malay archipelago, the Europeans include Americans, the Indians would be people from the Indian subcontinent including what would now be Pakistan and Bangladesh. In 1901, the total population of Singapore was 228,555, with 15.8% Malays, 71.8% Chinese, 7.8% Indians, and 3.5% Europeans and Eurasians. The Chinese population figure of Singapore has stayed at over 70% of the total since, reaching 77.8% in 1947. After dropping from a peak of 60% in the early years of Singapore, the Malay population would range between 11 and 16% in the first half of the 20th century, while Indians hovered between 7 and just over 9% in the same period.. How many times has Singapore conducted a thorough census since 1871?