I found this table of immigration to various countries - India is number 4 in the list
Table 1: Top ten countries for total immigration (1970-1995)
[1]CountryNet number of immigrants (millions
)............so here are the reasons:
United States 16.7 (worldwide immigration, mainly Latino)
Russian Federation 4.1 (return of ethnic russians to Russia after breakup of USSR)
Saudi Arabia 3.4( Influx of Pakistan/Indian/Bangladeshi/Phillipino/Western labour to fuel Saudi oil boom)
India 3.3 (Bangladeshi refugees, post 1971 war)
Canada 3.3 (worldwide immigration)
Germany 2.7 (Turkish)
France 1.4 (Algerian/French West Africa)
Australia 1.4 (Worldwide, mainly Europe, Vietnam, Lebanon)
Turkey 1.3 (mainly Iraqi Kurds)
United Arab Emirates 1.3 (as per Saudi Arabia)
Figures are the latest that I could find.