Mitt Romney didn't offer many new details about his immigration plan in his speech yesterday before a group of Latino officials. But he did reiterate his support for a few concrete measures, including a narrow version of the DREAM Act that would provide a path to legalization for immigrants who serve in the military. (You can read the outline of his plan here.)

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Such a measure would offer relief to a tiny proportion of young illegal immigrants. The Migration Policy Institute ran the numbers back in 2010, when Congress was deliberating a full version of the DREAM Act that had an age cut-off of 35 years. (Other versions have a cut-off of 30 years.) Of the 612,000 with a high-school degree or GED — typically a requirement for joining the military — only 5 percent, "about 31,000 people, would be likely to enlist in the military" and thus be eligible for legal status, says Jeanne Batalova, MPI's policy analyst. And that's just 1.5 percent of the 2.1 million illegal immigrants who would qualify for legal status under DREAM overall, including those without a high school diploma.

Why don't more illegal immigrants join the military? Most likely because the military aptitude test is only offered in English, and a significant proportion of young illegal immigrants are without the high school diploma that's required. That number could go up if legal status was an incentive for joining the military, but it's far from comprehensive.

By comparison, Obama's latest immigration policy could make up to 1.4 million eligible for deportation deferral, which has an age cut-off of 30 years. The policy doesn't offer a path to legal status, but it gives an indication of the pool of illegal immigrants that Obama wants to prioritize.