Which Indians have migrated - within and outside the country - the most

The migration of Indians beyond the borders of the country is well documented. Whether it's

Malayalis

in the

Middle East

, Sikhs in Canada or the UK, or Gujaratis in the US, there are certain communities that are associated with geographies due to large-scale migration over decades. They’re also associated with remittances from their adoptive countries that fuel the economy.
What’s less known is the scale of migration within the country in spite of it taking place over decades.