Dr. Mehmet Oz, the top official overseeing the Affordable Care Act (ACA), has warned that enrollment for the Obamacare system may be too high due to high monthly premiums. He believes millions of people may be fraudulently enrolled or eligible for other types of coverage. Despite this, the number of sign-ups for the ACA has dropped significantly this year due to increased costs. Oz believes some of the enrollment may be due to fraud in the sign-up process, duplicate coverage or tax credits they didn't qualify for. He expects further enrollment to fall to around 19 million. The administration has proposed changes to the ACA to bring more people into the marketplace.