Immigration is one of the leading ways a country grows. It can play a significant part in the economy of a country regardless of what the country is. Immigration tends to be more common is first world countries like the United States, Canada and some European countries.There are many reasons for immigration. Often when individuals or families immigrate to a first world country, they're doing so to try to create a better life for their families. Check out immigration for more. Other reasons for immigration could include natural disaster, family re-unification, or escape from political or economic upheaval.The International Organization for Migration keeps records of immigration. Europe, overall, tends to host the largest number of immigrants according to the organization. North America (US and Canada) is lumped together is sits in second place as far as the number of immigrants that come to the country. Perhaps surprisingly for some, Asia is in third place and hosts the next largest number of immigrants.According to the United Nations, there were nearly 191 million international migrants worldwide. Percentage wise this means that 3 percent of the world's population are migrants or immigrants. Developed countries tended to see the highest rate of immigration. Less developed countries saw a drop in immigrations due, according to the United Nations, to a fall in refugees. The UN expects that the number of people who will end up living in a country outside the one of their birth will increase in the future.There are theories surrounding why immigration happens. One theory is what's called the Push and Pull theory. Push factors refer to negative motives that cause individuals to basically flee the land of their birth. Wage rates can have an impact. Someone might leave the country of their birth for a job that pays better as long as the costs of the move isn't too high. Escape from poverty is a strong motivator of immigration. So is fleeing from events like natural disasters.The number of people immigrating to get a better job has increased. It's increased so much that someone immigrating to a new country for employment has a specific term, an economic migrant. The purpose of an economic migrant is to improve his or her financial position by seeking employment. An economic migrant is a distinct type of immigrant with very different reasons for immigrating than one who is a refugee fleeing persecution.To protect themselves, many countries restrict allowing someone to enter a country for the reasons of work without a valid work visa. It can and has happened where those who have declared themselves an economic migrant are refused entry into the country they're trying to get new work in.Immigration has been a hot topic in many countries. It's become a political issue in some countries especially regarding the treatment of migrant workers. Some countries try to encourage immigration more from the educated, skilled and wealthy. Click here for details.