verb
BAD : A lot of new doctors migrate to America where they can earn more money.
GOOD : A lot of new doctors emigrate to America where they can earn more money.
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migrate = (of birds, animals and people) travel from one place to spend a length of time in another, especially to find food, water, warmer weather, etc: 'How do birds know when to migrate and how do they find their way back home?'
emigrate = (of people) leave your own country and make your home in another one: 'There were no jobs back home so we decided to emigrate.'