Nearly two-thirds of the 5.4 million legal immigrants from Mexico who are eligible to become citizens of the United States have not yet taken that step. Their rate of naturalization—36%—is only half that of legal immigrants from all other countries combined, according to an analysis of Census Bureau data by the Pew Hispanic Center, a project of the Pew Research Center.

Creating a pathway to citizenship for immigrants who are in the country illegally is expected to be one of the most contentious elements of the immigration legislation that will be considered by Congress this year. Mexican immigrants are by far the largest group of immigrants who are in the country illegally—accounting for 6.1 million (55%) of the estimated 11.1 million in the U.S. as of 2011.

Mexicans are also the largest group of legal permanent residents—accounting for 3.9 million out of 12 million. The Center’s analysis of current naturalization rates among Mexican legal immigrants suggests that creating a pathway to citizenship for immigrants in the country illegally does not mean all would pursue that option. Many could choose an intermediate status—legal permanent resident—that would remove the threat of deportation, enable them to work legally and require them to pay taxes, but not afford them the full rights of U.S. citizenship, including the right to vote.

Read more at Pew Hispanic Research Center