“In some countries net immigration provides the only population growth. The United States is the third most populous nation in the world, behind China and India with a current population of 309 million. An estimated 4.3 million babies were born in the USA during 2007 and the population increased by an estimated 1.2 million people. According to the US Census Bureau projections, the US population could reach 422 million by 2050. The main growth in the population is through patterns of migration from Central and South America…”