There are numerical limits on the number of immigrant visas that can be granted to aliens form any one foreign country. This limit is the same for all countries. The limit is based on place of birth, not citizenship. Where the immigrant is "charged", means that person is counted towards a given country's numerical limit. For example, an immigrant born in Ethiopia is "charged" to Ethiopia, and therefore counted towards reaching the numerical limit for that country. The person would be "charged" to Ethiopia, even if the immigrant born in Ethiopia was born of Yemeni parents and has a passport from Yemen.