They all wanted Jonathan Gruber, a numbers wizard at M.I.T., to help them figure out how to fix their health care systems, just as he had helped Mitt Romney overhaul health insurance when he was the Massachusetts governor. Then came the call in 2008 from President-elect Obama’s transition team, the one that officially turned this stay-at-home economics professor into Mr. Mandate. Mr. Gruber has spent decades modeling the intricacies of the health care ecosystem, which involves making predictions about how new laws will play out based on past experience and economic theory. It is his research that convinced the Obama administration that health care reform could not work without requiring everyone to buy insurance. And it is his work that explains why President Obama has so much riding on the three days of United States Supreme Court hearings, which ended Wednesday, about the constitutionality of the mandate. Questioning by the court’s conservative justices has suggested deep skepticism about the mandate, setting off waves of worry among its backers — Mr. Gruber included. “As soon as I started reading the dispatches my stomach started churning,” Mr. Gruber said of the arguments on Tuesday, while taking a break from quizzing his son for a biology test. “Losing the mandate means continuing with our unfair individual insurance markets in a world where employer-based insurance is rapidly disappearing.” Mr. Gruber, 46, hates traveling without his wife and three children, so he is tracking the case from his home in Lexington, Mass. There he crunches numbers and advises other states on health care, in between headbanging at Van Halen concerts with his 15-year-old son and cuddling with the family’s eight parrots. (His wife, Andrea, volunteers at a bird rescue center.) If the court rules against the mandate, Mr. Gruber says he believes the number of newly insured Americans could fall to eight million from the projected 32 million. He insists that without a mandate, the law will result in a terrible spiral: only relatively sick Americans will choose to get insurance, leading premium prices to rise and causing the healthier of even those sick people to drop their insurance, sending prices higher and higher. Some other economists quibble, though, with Mr. Gruber’s pessimistic assessment. “My general thought about the mandate is if insurance is affordable and accessible, most people will buy it anyway,” said David Cutler, an economist at Harvard and longtime collaborator of Mr. Gruber’s. Others, like Paul Starr, a Princeton sociologist, say they believe Mr. Gruber’s work does not account for how hard it will be to enforce the mandate. “There is this groupthink about how important the mandate is,” Mr. Starr says. “Most people don’t understand or won’t acknowledge how weak the enforcement mechanism is.” Mr. Starr said he thought Mr. Gruber in particular was overstating the effectiveness of the mandate because “it’s his baby.” That said, it is difficult for too many other experts to categorically refute Mr. Gruber’s work, since he has nearly cornered the market on the technical science behind these sorts of predictions. Other models exist — built by nonprofits like the RAND Corporation or private consultancies like the Lewin Group — but they all use Mr. Gruber’s work as a benchmark, according to Jean Abraham, a health economist at the University of Minnesota and former senior economist in both the Obama and George W. Bush administrations. “He’s brought a level of science to an issue that would otherwise be just opinion,” Mr. Cutler says. “He’s really the only person who has been doing all this careful modeling for so long. He’s the only person you can go to for that kind of thing, which is why the White House reached out to him in the first place.” Mr. Obama had made health care reform a cornerstone of his campaign, and wanted to announce a credible proposal quickly after taking office. But members of the Obama administration’s transition team said they had inherited an executive branch that had vastly underinvested in modeling research on health care, especially compared to the technical modeling that had been done in areas like tax policy. “Creating a good model from scratch would have taken months, maybe years,” said Lawrence H. Summers, who was the director of President Obama’s National Economic Council and had advised Mr. Gruber on his dissertation when they were at Harvard. Mr. Gruber had already spent years researching government mandates, starting with his 1991 dissertation about how mandated employer benefits cut into workers’ wages.
