Immigration is one of the driving factors when it comes to population growth in developed and developing nations; the United States is no exception. Former American president, Bill Clinton once famously said, "the United States has always been energized by its immigrant populations." Things have changed considerably since then. Immigration, which was then given the credit for sculpting the diversity of the United States, is now being accused of fueling cultural turmoil and threatening the American culture. After a brief slump during the recession period, the number of illegal immigrants in the United States is once again on rise. As of March 2012, it had reached 11.7 million from 11.3 million that it was in 2009. While that has once again brought to the forefront the age-old debate on how immigration is affecting the American way of life, we thought a better thing would be to stay out of it and focus on numbers instead. The ups and downs of immigration in the United States can be traced back to the 18th century. As for 'downs', the Great Depression is by far the best example of the same. In 1933, the total number of immigrants who came to the United States was 23,068, down from 279,678 immigrants that came in 1929. This was the period when the number of people who emigrated from the US was more than those who immigrated. In 1965, amendments to the 1952 Immigration and Nationality Act (INA) abolished the quota system, which formed the basis of immigration based on nationality. This resulted in large-scale immigration from non-European countries―a relatively new trend in America. As a result of this, the total number of European immigrants in the United States, which accounted for 60 percent in 1970, came down to 15 percent in 2000. Between 2000 and 2010, 14 million immigrants entered the United States, and the number of immigrants―both, legal and illegal―reached 40 million. The number of first generation immigrants in the country increased dramatically from 9.6 million in 1970 to 40 million within a span of four decades. According to 2011 American Community Survey carried out by the US Census Bureau, the total number of immigrants in the US was 40.4 millions; accounting for 13 percent of the total US population. Mexico―accounting for 11.7 million immigrants―topped the list, and was followed by India (1.9 million), Philippines (1.8 million), and China (1.7 million). According to the US Department of Homeland Security (DHS), 757,434 individuals were naturalized in 2012. Once again Mexico accounted for the biggest share at 13.5 percent, followed by Philippines and India accounting for 5.9 and 5.4 percent respectively. In 2006, the number of legal immigrants accepted as permanent residents in the United States exceeded the number of such migrants accepted by all other countries put together. According to the DHS estimates, around 11.5 million undocumented immigrants were residing in the United States in the beginning of 2011. While that was a decline from 11.6 million in 2010, recent estimates show that illegal immigration is on rise once again; the figure has reached 11.7 million as of March 2012. Mexico dominates yet another list―this time for the wrong reason though―with more than half the illegal immigrants to its credit. Latin Americans make up 22 percent of the illegal immigrants in the United States, and Asians 13 percent. The 2,000-mile United States-Mexico border has been notorious for the ill-practice since a long time. Over the last three decades, the federal administration has introduced as many as seven amnesties for illegal migrants. In 2009, the federal administration granted legal resident status to around 1.1 million immigrants in its efforts to curb various illegal immigration problems. Note: Illegal influx of immigrants from the neighboring countries has definitely been one of the major concerns for America. However, it is very difficult to monitor such influx, and thus, one has to rely on estimates to get a rough picture. Going by the Gallup survey, which shows that 1 in 30 adults worldwide would prefer to settle in the United States, it becomes pretty clear that the immigration trend is not going to reverse any time soon. If the United States Census Bureau estimates are to be believed, the US population is expected to reach the 397-million mark by 2050 if immigration continues at the ongoing rate.