Barack Obama should be more explicit about how he wants people to pay for health insurance under his plan—but don't hold your breath for more details.

That's the opinion of Jonathan Gruber, an MIT economist who helped to develop the health care plans of Hillary Clinton and Barack Obama. Gruber said that after Clinton's proposal to cap health insurance premiums at 5 percent to 10 percent of income, the onus has moved to Obama to detail how much he thinks Americans should pay for health insurance.

"I think it helps if they both have real numbers," said Gruber. "I think having one person having a number doesn't help that much, because then you can't really compare."

When asked if the onus was now on Obama to detail how Americans would pay for insurance, Gruber said "Yeah I think so." But when asked if he thought the Obama campaign would actually provide that number, he was doubtful. "No," he said. "They're the front-runners. Front-runners don't produce numbers."  read more »