Pew Hispanic recently released a study entitled "U.S. Unauthorized Immigration Flows Are Down Sharply Since Mid-Decade" (link). There are links to two previous studies with similar findings by the Department of Homeland Security and the Center for Immigration Studies here.

According to Pew's study:

The annual inflow of unauthorized immigrants to the United States was nearly two-thirds smaller in the March 2007 to March 2009 period than it had been from March 2000 to March 2005...

...This sharp decline has contributed to an overall reduction of 8% in the number of unauthorized immigrants currently living in the U.S. - to 11.1 million in March 2009 from a peak of 12 million in March 2007, according to the estimates. The decrease represents the first significant reversal in the growth of this population over the past two decades...

...Even though the size of the Mexican unauthorized population living in the United States has not changed significantly since 2007, the inflows from that country have fallen off sharply in recent years. According to the center’s estimates, an average of 150,000 unauthorized immigrants from Mexico arrived annually during the March 2007 to March 2009 period - 70% below the annual average of 500,000 that prevailed during the first half of the decade...

A few notes:
1. Only two months covered by their study were during the Obama administration; if you see someone claiming this has something to do with Obama immigration, leave a cite in comments.

2. The decline preceded the current economic downturn and coincided with George W Bush somewhat ramping up enforcement as part of his attempt to push comprehensive immigration reform.

3. However, the study notes that "Nearly half of unauthorized immigrants living in the country in 2009 - 47%, or 5.2 million people - arrived in 2000 or later." The responsibility for all of those illegal aliens lies with Bush; his proxies from Michael Chertoff to Michael Gerson; other "Bushies" such as his brother Jeb Bush; and his current and former supporters. Those who currently push the "Miss Me Yet" line should be constantly publicly reminded of that statistic.

4. The study notes that "Mexico accounted for 60% of unauthorized immigrants in 2009, or 6.7 million people. Other Latin American nations accounted for 20% of the total, or 2.2 million people. South and East Asia accounted for 11% of the total, or 1.2 million people." A minor talking point used by illegal immigration supporters is to claim that few on the pro-enforcement side talk about European illegal aliens; remind them of that statistic.

5. And: "In 2009, 59% of unauthorized immigrants resided in California, Texas, Florida, New York, Illinois and New Jersey. However, the share living in those states has declined from 80% in 1990, as unauthorized immigrants have dispersed to new settlement areas." That helps explain why politicians in non-border states attempt to pass pro-enforcement bills. Note that some illegal immigration supporters question why someone in, say, Massachusetts might be concerned about this issue; confront them with that statistic.

6. And, another statistic Bush and his unrepentant supporters are responsible for: "The number of children who are unauthorized, 1.1 million in 2009, declined slightly over the decade. By contrast, the population of U.S.-born children with at least one unauthorized parent nearly doubled from 2000 to 2009, when they numbered 4 million." The far-left and related groups work very hard to prevent illegal aliens in mixed-status families from being deported, and Bush made the situation far worse.

7. And: "States with the largest shares of immigrants in the labor force are Nevada (9.4%), California (9.3%), Texas (8.7%) and New Jersey (8.7%)... The unemployment rate for unauthorized immigrants of all ages in March 2009 was higher than that of U.S.-born workers or legal immigrants - 10.4%, 9.2% and 9.1%, respectively." If we deported all of them tomorrow, not every one of those jobs would be immediately filled by an unemployed American, and the economy would suffer further due to the loss of consumers. However, it would would free up jobs for Americans and if done over time wouldn't have as great an economic impact, offset by less spending. Make that argument to illegal immigration-supporting and -enabling politicians to their face on video and hold them responsible.

8. The study provides more evidence in support of attrition: the illegal alien population in the U.S. isn't fixed; with increased enforcement the numbers could be reduced even further.