White House press secretary Sean Spicer arrives for the daily press briefing at the White House on Wednesday. JIM WATSON/AFP/Getty Images

Congress’ official scorekeepers still aren’t finished assessing how much Republicans’ new health care bill will cost or how many people it will leave uninsured, but that’s not stopping the GOP lawmakers from plowing ahead anyway.

Republicans’ clipped timeline – including Wednesday’s committee meetings on the bill before the Congressional Budget Office releases its projections of what the measure will do – is part of a GOP effort to swiftly deliver on its promise to repeal and replace Obamacare.

But it also marks a sharp departure from Congress’ last health care reform battle, the 2009-2010 debate over Obamacare in which both parties continually cited the office’s reports to make their case. “When we were writing the ACA, we didn’t say, ‘Boo,’ without thinking about what the CBO would say,” said Jonathan Gruber, a senior health care adviser to the Obama administration.

This time around, however, Republicans aren’t only moving ahead without the CBO’s input, they’re looking to undermine the office before its report comes out.

“The irony of the score is that the CBO was way off last time,” White House press secretary Sean Spicer said Wednesday when asked about moving forward without the bill. “If you’re looking at the CBO for accuracy, you’re looking in the wrong place. The idea that that’s any kind of authority based on the track record of what happened last time is a little far fetched.”

So how did CBO do at assessing Democrats’ Affordable Care Act?

In general, the office had hits and misses in its assessment, predicting the measure would cost more than its eventual price tag but also estimating it would expand access to health insurance to more people that it eventually did.

Coverage

The CBO’s most serious mistake was arguably overestimating Americans who would receive insurance for the first time under Obama’s reforms.

During the debate over the law, the office projected that just 21 million Americans would be uninsured by last year. In fact, there were still about 27 million without insurance, according to preliminary data from the federal Centers for Disease Control and Prevention.

The CBO at first projected that eventually as many as 32 million more people could obtain coverage. So far, only about 13 million more have done so, according to the nonpartisan Kaiser Family Foundation, and the CBO has repeatedly revised its forecast downward.

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The CBO was not expecting the Supreme Court to rule that states could decide for themselves whether or not to cover more people through Medicaid. Many poor residents of Republican states whom the office was expecting to become insured never received coverage.

While the Supreme Court’s ruling contributed to the discrepancy, the CBO also underestimated the number of people would sign up for the program in the states where Medicaid was expanded. Meanwhile, in the rest of the country, the public attention to health insurance generally encouraged an unexpected increase in enrollments in Medicaid.

On the whole, there are about 15 million more people enrolled in Medicaid than there would have been without the Affordable Care Act’s changes, according to recent federal data — a figure that comes close to the initial CBO estimate.

More than Medicaid, it’s the online exchanges established under the law that account for it falling short of CBO projections.

That original estimate projected that 23 million people would purchase insurance through the exchanges this year. The figure will only be 12 million, according to the most recent federal data.

“I don’t think that CBO is above criticism,” said Douglas Elmendorf, who was the agency’s director during the initial debate.

In his view, he and his colleagues assumed that fewer people would be willing to pay the penalties associated with going without coverage under Obama’s reform than in fact were, and that they the financial help available to purchase insurance would encourage more people to enroll than ultimately did.

“The principal thing that CBO mis-estimated in its original estimates for the Affordable Care Act was the potency of the mandate and penalties,” he said. “The stick of the penalties and the carrot of the subsidies turned out to be less effective than we expected.”

Premiums

The ACA created a system where people could purchase health insurance without needing to go through their employers. Though the vast majority of Americans still get their coverage either from employer-sponsored plans or directly from the government, these health insurance marketplaces offer an important lifeline for those who can’t buy health insurance any other way.

The premiums offered on these marketplaces were initially lower than the CBO predicted. The average cost of a silver-level plan in 2014 was $3,800, about 19 percent less than what the CBO projected in 2010. Some believed that competition was driving prices down. Others thought that insurance companies were setting prices that were unsustainably low.

Since then, premiums have started to rise, turning the exchanges into a topic of controversy. For 2017, the cost of the most popular silver-level plans increased by an estimated 25 percent, according to the Department of Health and Human Services.

But in a way, these trends vindicate the original predictions of the CBO, Gruber argued. The price of health insurance on the exchanges is now approaching what the CBO projected some seven years ago. “Everyone talks about the big premium increases last year, but they don’t acknowledge that premiums started out way lower than we thought,” Gruber said. “The CBO’s premium forecasts were incredibly accurate for 2017.”

Obamacare’s price tag

All of this means Obama’s reform has cost less than the CBO expected at first.

Fewer people are enrolled in the exchanges, so fewer people are receiving financial help from the government to buy insurance. The premiums for insurance have been less expensive, so those who are getting help need less of it.

In 2010, the CBO projected that net expenditures on coverage under Obama’s reform last year would total $132 billion. The total the office estimated last year was just $110 billion.

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Obama’s plan has come in under budget. Meanwhile, though, some of the planned sources of funding for the reform have not materialized, either.

In 2015, for instance, Congress delayed a tax on the most expensive health-insurance plans, known as the “Cadillac tax.” The middle class holds many of the policies that would have been subject to the tax, especially members of unions with generous health-insurance plans sponsored by their employers.

At the same time, Congress suspended a tax on some medical devices and declared a holiday for certain fees paid by insurance companies. In all, the changes were expected to eliminate $30 billion in funding over a decade.

Elmendorf noted, though, that the CBO was more accurate than many other forecasters at the time, who predicted an explosion in federal spending.

“In 2009 and ’10, both the Democratic and the Republican leadership in the Congress respected CBO’s role in the process,” Elmendorf said. “I hope and believe that current Republican and Democratic leadership in the Congress will respect CBO’s work during this discussion.”

The verdict…

The CBO’s struggles in projecting the Affordable Care Act’s effects underscore the difficulty of predicting the future of any bill, particularly one that depends both on the performance of the economy as a whole and on future decisions made by Congress and the administration.

The political obstacles to actually collecting any taxes that are enacted, along with the mathematical challenges of predicting how an extraordinarily complicated system like the health care sector will respond to changes in policy, mean that the CBO’s forecasts may miss the mark this time as well, said Tom Miller, an economist at the conservative American Enterprise Institute.

He agreed that the office has a record ofimprecise forecasts, but he said that is only to be expected. “We’re peering into the CBO’s crystal ball which is a little cloudy,” he said. “Now it doesn’t mean that you should ignore it completely. It’s more information … I wouldn’t say that you should close your eyes to this — that’s silly — but you shouldn’t believe it verbatim either.”

Gruber, who advised the Obama administration, defended the agency’s role in the debate. “The CBO plays an incredibly important role in keeping the discussion honest. Once you don’t care what the CBO says then you can just make up your own numbers, and it’s the end of democracy,” he said.

And while Spicer and other Republicans knocked the office, other members of Trump’s administration are predicting the CBO will come down firmly on their side. Mick Mulvaney, Trump’s budget director, even suggested in an interview with MSNBC on “Morning Joe” Wednesday morning that a favorable score was a foregone conclusion.

“I hear all the talk about the CBO score,” Mulvaney said. “The only question about the CBO: Is it going to be really good or is it going to be great when that number finally comes out?”