The highest point in Indian migration to Great Britain occurred between 1955 and 1975. One of the main reason that prompted Indias to migrate was the strong economic attraction of the destination, as the currency conversion rate between the British Pound and the Indian Rupee was hugely favorable to the latter. There was also a "status" competition among people from the communities who decided to migrate, who saw living in Great Britain as an upgrade in social status.
Two things that increased american interchanges in the late 1800s were "b. the telegraph and telephone," since both of these creations significantly accelerated correspondence and made it more productive.