The nation's uninsured rate dropped modestly this month as the major coverage expansion under President Barack Obama's health care law got underway, according to a closely watched survey released Thursday. The Gallup numbers could be the first evidence that core provisions of Obama's much-debated law have started delivering on the promise of access for nearly all Americans. The Gallup-Healthways Well-Being Index found that the uninsured rate for U.S. adults dropped by 1.2 percentage points in January, to 16.1 percent. The biggest change was for unemployed people, a drop of 6.7 percentage points. That was followed by a 2.6 percentage-point decline for nonwhites.