11 Million Strong: Counting America's Undocumented Immigrants

What's the plan for America's 11.1 million undocumented immigrants?

It's the million dollar question, and the most divisive element of the Senate's sprawling new effort to overhaul the country's messy immigration system. After months of painstaking negotiation, a bipartisan group of senators, known as the "Gang of Eight", recently unveiled a proposal to -- among other things -- create a path to citizenship for the millions who live here in the shadows. But legislators have made abundantly clear that this proposal is a far cry from "amnesty". The path they outlined for almost all the undocumented (except for young "DREAMers" who would be on a streamlined 5-year path) is a tedious, decade-plus-long process full of steep hurdles and strict conditions, in which citizenship is a distant destination at the end of a long journey.

Where do the undocumented live?

The following map, produced by the online magazine Slate, uses the most recent Pew Research Center analysis of 2011 data, which includes state-by-state estimates. Slate notes that the data meets the 90-percent confidence interval for population estimates for each state (except for the handful of states where the undocumented immigrant population is so low that it's nearly impossible to confidently estimate).

Many more undocumented immigrants reside in California (topping 2.5 million) and Texas  (more than 1.5 million)  than any other state, according to Pew data. However, Nevada has the largest proportion of undocumented immigrants—7.2 percent of the state population and nearly 10 percent of its workforce.

Mouse over each state to see the estimated number of undocumented immigrants living there, what percentage of the total state population and workforce they make up, and how the number of undocumented immigrants has changed over the past two decades.

Editor's note: since production of the map, most media organizations have begun referring to this population as "undocumented" rather than 'illegal" immigrants.

What else do we know about undocumented immigrants in the U.S.?

• The population has actually gone down quite a bit since 2007, when it spiked at about 12 million, according to Pew. The decrease is due largely to the U.S. recession and increased border enforcement and deportations, with the rate of undocumented immigration from Mexico falling the most.
• Mexicans made up close to 60 percent of all undocumented residents, according to a Pew analysis of the 2010 population. DHS estimates that in 2011, 70 percent of this population came from Mexico, Guatemala and El Salvador.
• Today's estimated 11.1 million undocumented immigrants make up less than a third of all foreign-born residents in the U.S. Roughly 40 to 50 percent of the undocumented entered the country legally and overstayed their visas, according to a Pew 2006 analysis. And although about 1.6 million of the total undocumented population today arrived within in the last years , the majority of the current population has lived here for at least a decade, reports the Department of Homeland Security reports.

So how do we know all this?

Counting America's undocumented population is a true exercise in estimation. Pew, a non-partisan public policy group, came up with the latest 11.1 million figure (for 2011) primarily by analyzing census data, which provides a measure of the total immigrant population (both legal and undocumented). Pew then analyzed a variety of other government data sources - including DHS - to estimate the number of legal immigrants (green card holders and refugees) and then subtracted this figure from the total number of immigrants. Of course, a lot more statistical wizardry goes into the calculation (as described here) but this is the basic framework for its estimation.