The following is a timeline of the growth of Mumbai's population over the last four centuries:
1661: 10,000 inhabitants
1664: 15,000
1673: 60,000 (Fryer)
1675: 60,000
1718: 16,000 (Cobbe)
1744: 70,000 (Niebuhr) (large influx of people during the busy season)
1764: 140,000 (Niebuhr), According to Historical account pg 6, pop was 60,000
1780: 100,000 Materials etc. Part III, pg 525 -- Mahim 13,726
1812: 235,000 (Hall) Fixed 165,000, migratory 50,000, famine increase 20,000
1814: 180,000 (Warden)
1830: 229,000 Lagrange
1836: 236,000 "-do-
1864: 816,562
1872: 644,605 (census)
1881: 773,196 (census)
1891: 821,764 (census)
1901: 812,912 (Greater Bombay)
1911: 1,018,388
1921: 1,244,934
1931: 1,268,936
1941: 1,686,127
1951: 2,966,902 (0.1% of the world population)
1961: 4,152,056
1971: 5,970,575
1981: 8,227,382
1991: 9,900,000 + 2,600,000 (Thané) = 12,500,000 (Greater Bombay)
2001: 16,368,084 (Greater Mumbai, incl. Thané)
2005: 18,366,088 (Greater Mumbai, incl. Thane)