Analysts at the Centers for Medicare & Medicaid Services assumed a year ago that the public exchange system would take in just 4.3 million applications during the 2013-14 open enrollment season.
CMS officials included that estimate in a routine paperwork review filing for exchange helper certification programs.
Around Oct. 1, when the first Patient Protection and Affordable Care Act open enrollment period began, officials at the U.S. Department of Health and Human Services declined to say how many people they expected the exchanges to enroll in commercial qualified health plans or government plans.
Many exchange watchers used a projection of 7 million, from the Congressional Budget Office, as a benchmark.
But CMS itself used the 4.3 million application figure back in July, when it was estimating how many navigators, or official, PPACA-required ombudsmen, and non-navigator assistance personnel, it would need to help consumers.
HHS reported in January that all state-based and HHS-run exchanges combined received 4.3 million coverage applications for 5.1 million people from Oct. 1 through Dec. 28.
HHS stopped releasing application totals, saying it believed enrollment system problems made the numbers unreliable.
But HHS said in March that the exchanges received plan selection information, not just applications, for 4.2 million people by March 1, and it said Tuesday that the public exchanges had received plan selection for more than 7.1 million by March 31.
From Oct. 1 through Dec. 28, exchanges were determining an average of 1.2 people eligible for coverage for each application received. If a similar ratio held true through March 31, the exchanges may have received about 5.9 million applications, or 37 percent more than CMS expected.