So the number "13" apparently is bad luck for Obamacare, too.
Federal officials on Monday sought to lower expectations for upcoming enrollment in Obamacare, announcing that they now believe that only between 9 million and 9.9 million people will be enrolled in Affordable Care Act health insurance plans by the end of 2015.
That is well below the 13 million people that the Congressional Budget Office has projected for Obamacare enrollment by the end of 2015. Open enrollment for 2015 plans resumes Saturday.
The new projection, as much as 30 percent reduced from the CBO estimate, comes from the Health and Human Services Department, which oversees the Obamacare health reform program.
HHS also said it now appears that it will take longer—perhaps quite a bit longer—than 2017 to reach a "steady state" of 25 million Obamacare enrollees that CBO had been projecting for 2017 enrollment.
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The reduced projection is due to recent data showing "mixed evidence" about how quickly—and how dramatically—people will shift from employer-sponsored health insurance and non-Obamacare plans into insurance plans sold on government-run marketplaces such as HealthCare.gov, according to HHS.
HHS noted that the Congressional Budget Office had assumed there would be "significant shifts over three years" from people in employer insurance and in so-called "off-Marketplace" individual plans.
But now, given new data, "there is considerable uncertainty that a large shift will occur over the new two years," HHS said in a report about the new projection. "This contributes to an analysis that the ramp up to 25 million will take more than three years."
"I wouldn't characterize it as an error," said an HHS official during a conference call with reporters when asked why the CBO numbers are so different from what HHS is now projecting. The official, who spoke on the condition of not being identified, said HHS was working off data that was more recent that what CBO had used for its projections made in April.
HHS also said Monday that there are about 7.1 million people currently enrolled in Obamacare plans.
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HHS said it assumes that 83 percent of current enrollees, or 5.9 million people, will renew coverage for 2015.
The department also said that by the close of open enrollment on Feb. 15, it expects a total of between 10.3 million and 11.2 million will be signed up for Obamacare plans, but expects that number to drift lower by the end of 2015.
HHS did not say how long it believes it will take to get to the 25 million enrollee projection made by CBO last April.
"We have not come up with our own a steady state estimate yet," an HHS official said. "It's going to take longer than three years."
"In the early years of any new program, there is a high degree of uncertainty about projections; actual enrollment could be significantly higher or lower," the department noted in its report.
The department also said it believes that most of the new enrollment in Obamacare plans for 2015 "is likely to come from the ranks of the uninsured."
The department's analysis projects there will be about three to four previously uninsured new enrollee for each new enrollee who comes from people who had had individual plans sold off the Obamacare exchanges.
The downward revised enrolled projections were met with disdain from a leading Congressional Republican, whose party has relentlessly criticized Obamacare for years.
"After years of broken promises and a painfully flawed launch, the administration is again trying to rewrite its definition of success for the president's signature law on the eve of Saturday's second enrollment," said House Energy and Commerce Committee vice-chairman Marsha Blackburn, R-Tenn "Last year, while cancellation notices were outnumbering new enrollments, the administration completely abandoned enrollment as a measure of success."
"No matter how you dress it up, bad policy is bad policy," said Blackburn. "Before administration officials takeout the Champagne again to celebrate its now downgraded measure of enrollment success, it needs to once and for all be transparent with the American people about the reality of this law."
HealthCare.gov and the 15 Obamacare exchanges run by the District of Columbia and individual states first began operations in October 2014. After two months of disastrously low enrollment as a result of technical problems on HealthCare.gov, enrollment strongly picked up in the first quarter of 2014.
By the close of open enrollment last April, there were about 8.1 million people enrolled in Obamacare plans.
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That number has fallen by about 1 million since then, as result of people either failing to pay their premiums, obtaining insurance elsewhere, being removed from the insurance rolls because they lacked proof of citizenship or legal immigration status, or other reasons.
Most current Obamacare enrollees will be automatically re-enrolled in their current plans, unless they opt for another plan.
-By CNBC's Dan Mangan