The best answer from the ones mentioned is the last one: encomienda. Encomienda is a system where the stronger partner provides protection to the weaker one in exchange for goods and services.
A large number of the European migrated to the America in search of the job opportunities and considered to be about 20% of the migration. While others migrated for the political stability and form 1500 to mid 20th century about 65 million left Europe.
