Obamacare is reducing the number of Americans without health insurance. And while nobody can say for sure exactly how many people are getting coverage, Gallup just provided a pretty big clue.

According to the organization, the proportion of adults without coverage last month fell to 13.4 percent. That's lower than it was last year. That's lower than it was when the Affordable Care Act became law—and when President Obama took office.

In fact, that's lower than it's ever been since the beginning of 2008, before the economic crisis, which is when Gallup started taking regular monthly polls on this question.

As always, you shouldn't take the specific figure too seriously. Polling on insurance status is really, really difficult. The most definitive, reliable information comes from government surveys and academic studies, the kind that won't be available for many months. The real rate of uninsurance among adults could be higher or lower. So could the magnitude of the change.