How migration brain drain impact the countries of migrants’ origin?

In my opinion, it impacts them a great deal. Countries of migrants' origins are usually the ones that are poor or where economy is declining so people with high education or wanted jobs migrate in wealthier countries leaving their homes. Every single expert which leaves a country where there is already not much experts, leaves a large loss for that country and its human capital. For a country that already lacks doctors, every next medic that leaves means prolonged waitlists in clinics, quality of service diminshed and public health in general affected. For every competent teacher leaving the state there are at least 100 potential students that won't be able to learn from him and maybe one day want to be him, and without education there is no progress in any field , so the only way is backwards, not progress.