The second open enrollment period under the Affordable Care Act began on Nov. 15, 2014, giving millions of Americans another opportunity to buy health insurance through online federal and state marketplaces. Enrollment has proven strong, with nearly 6.8 million people signing up for health insurance on the federally operated exchange alone as of Jan. 9, 2015. The exchange, which supports enrollment for residents of 36 states, has not surprisingly had the greatest number of registrations from the two highest-population states that do not have their own marketplace: Florida (1,190,922) and Texas (859,377). But three other states have also each enrolled roughly 400,000 people.

Behind the numbers
Nearly 7 million people enrolled in Obamacare during its first open enrollment period, and this week's update from the Department of Health and Human Services suggests enrollment will handily outpace that number this time around.

The results so far are encouraging to insurers, including UnitedHealth Group (NYSE:UNH) and Anthem (NYSE:ANTM), that bet enrollment would rise even if health care plan prices headed higher.

When open enrollment ends on Feb. 15, UnitedHealth could prove to be the leading beneficiary of this surge in enrollment because it's offering exchange plans in nearly two dozen states, including each of the top five states for health enrollment this year: Florida, Texas, North Carolina, Pennsylvania, and Georgia. StatesCumulative Plan Selections
  Nov 15 – Jan 9
Florida 1,190,922
Texas 859,377
North Carolina 434,503
Pennsylvania 408,934
Georgia 398,781
Virginia 298,981
Michigan 290,439
Illinois 272,623
New Jersey 202,732
Missouri 197,539
Ohio 186,232
Indiana 175,447
Tennessee 172,530
Wisconsin 169,704
Arizona 160,466
South Carolina 150,962
Louisiana 126,454
Alabama 126,061
Utah 109,218
Oklahoma 95,165
Oregon 84,360
Mississippi 76,005
Kansas 75,836
Maine 59,126
Nebraska 57,479
Arkansas 52,364
Nevada 47,784
Montana 45,278
New Hampshire 44,976
New Mexico 40,972
Iowa 34,586
West Virginia 26,236
Delaware 19,338
South Dakota 17,196
Wyoming 17,029
Alaska 15,830
North Dakota 14,973

Source: HHS

Rising tide
In Florida, 983,775 people signed up for health insurance through health during the first open enrollment period, which ran from Oct. 15, 2013, through March 31, 2014. That means enrollment in the Sunshine State during the current open enrollment period is already up more than 20% from the last time around -- with another four weeks to go. Perhaps even more notable about that significant increase -- at least from the insurers' perspective -- is that growth came despite health insurance plan prices increasing by an average of 7% in Florida during this enrollment period versus a year ago, according to the Commonwealth Fund.

Source:Governor of Texas Flickr.

Similarly, Texas' enrollment is also running higher than the 733,000 who signed on through health the first time around. That means that despite health insurance plan prices increasing 5% in the Lone Star State (per the Commonwealth Fund), enrollment is still on track to climb by 17.2%. 

Meanwhile, insurance enrollment via health in North Carolina, Pennsylvania, and Georgia looks set to grow by 21%, 28%, and 26%, respectively.

Measuring the impact
Exchange enrollment figures suggest the administration has a good shot at exceeding the 9 million enrollment prediction it made in November for the federal and state exchanges. If so, insurers and their investors could profit handsomely this year. According to the Commonwealth Fund, the average national silver-level exchange plan (the most common tier selected by enrollees) will cost a 40-year-old nonsmoker $314 per month, or $3,768 for 2015. That means that insurers are likely to post billions of dollars in premium revenue growth this year.