350 billion. Tremendous increase in the size and growth of the population is called population explosion. Human World Population [table] Year | Population ; 1700 AD | 0.6 billion ; 1850 | 1 billion ; 1930 | 2 billion ; 1965 | 3.5 billion ; 1975 | 4 billion ; 1990 | 5 billion ; 2000 | 6.1 billion ; 2011 | 7 billion [/table] Population of India 1901-2011 [table] Year | Population ; 1901 | 238, 396, 327 ; 1911 | 252, 093, 390 ; 1921 | 251, 321, 213 ; 1931 | 278, 977, 238 ; 1941 | 318, 660, 580 ; 1951 | 361, 088, 090 ; 1961 | 439, 234, 771 ; 1971 | 548, 159, 652 ; 1981 | 685, 148, 692 ; 1991 | 843, 930, 861 ; 2001 | 1,027, 015, 247 ; 2011 | 1,210, 193, 422 [/table]