Let's step back from the abnormality of a national leader calling other countries "shitholes," as U.S. President Donald Trump apparently did while complaining the United States got too many immigrants from Haiti and poor African nations and too few from countries "like Norway." He probably spoke — as he often does, in his damn-the-consequences way — for many others, Americans as well as Europeans.
As one of some 257.7 million people not living in the countries of their birth today, I have something to tell these people: Your own countries could quickly lose their standing in the world if you try to limit immigration to people from the wealthier nations.
Trump has probably never traveled to the countries he's insulted, but I suppose he means they're poor and/or unhappy. Various rankings could sort out qualifying countries on those terms — by per capita economic output, freedom level or some composite indicator like quality of life or happiness. But since we're discussing migration, none quite work. From a migration point of view, the worst countries are those where the greatest percentage of the population has the desire and ability to vote with its feet. For example, North Korea is, by most definitions, not a nice country, but its borders are sealed. And Norway — to use Trump's example — is a wealthy, happy country, but a relatively large number of Norwegians — almost 200,000, according to the United Nations, or 3.7 percent of the country's current population — live overseas.