President Obama said on Friday that the 4.2 million enrollments in Obamacare so far were likely sufficient for the law to work, according to the Associated Press. He might want to hold off on that prediction — at least until everyone pays. 

During an interview with Web MD, the president said the number "is already large enough that I'm confident the program will be stable." For insurers to be able to cover people who are sicker at lower premiums, it needs more healthy people to pay into the system. The president acknowledged that the percentage of young enrollees — who he has been reaching out to with Funny or Die videos and celebrity endorsements — is more important to the law's economics.

But he didn't acknowledge questions over whether that 4.2 million figure is inflated. As several sites have reported in recent weeks, that figure includes people who have not paid for the plans they've signed up for. The administration has said in the past that they don't know how many people have actually paid, but insurance companies estimate it is somewhere between 15 to 20 percent. That means the actual number of participants in the program could be 630,000 to 840,000 fewer. 

March 31 is a key deadline for Obamacare: anyone who hasn't been covered for the first three months of 2014 will have to pay the individual mandate penalty. The White House expects numbers to climb, and after adding March enrollments and subtracting the number of people who chose a plan but never paid, the number will likely be higher than 4.2 million. But that's still a long way from the seven million the administration originally hoped to sign up by the March deadline. 

It's likely the administration already has the data on payments, but hasn't compiled it. As one source told Politico:

“They have a lot more information than they’re letting on,” one industry source said of the Obama administration. “They have real hard data about the percent that have paid … If they have not processed those yet and compiled the data, that is a choice they are making. But they have that data now.”

If that is the case, Obama may feel comfortable in his assertion to Web MD regardless of the public information. If it's not, he may be speaking prematurely.