About 2 million people fewer than previously projected will pay Obamcare's penalty for not having insurance in 2016, according to a revised estimate from federal budget scorekeepers.

About 4 million people in 2016 are expected to pay the penalty for skipping health insurance, the Congressional Budget Office and the Joint Committee on Taxation say in a new report. That's down from 6 million in their September 2012 projection, mostly because of an increase in those who qualify for an exemption from the individual mandate.

The CBO/JCT projects 30 million people will still lack coverage in 2016, but 23 million will qualify for at least one exemption. They also think it will be hard to collect the mandate penalty from some people. They write:

Among the uninsured people subject to the penalty, many are expected to voluntarily report on their tax returns that they are uninsured and to pay the amount owed. However, other people will try to avoid payments. CBO and JCT’s estimates of the number of people who will pay penalties account for likely compliance rates as well as the ability of the Internal Revenue Service (IRS) to administer and collect the penalty payments.

The penalty in 2014 starts at $95 for an adult or 1 percent of taxable income, whichever is greater. That climbs to $325, or 2 percent, in 2015; and $695, or 2.5 percent, in 2016.

The CBO/JCT also expect people earning more than 400 percent of the federal poverty level — the cut-off point for federal tax credits to purchase coverage on Obamacare exchanges — will pay the greatest share of the penalty in 2016.

Actual enforcement of the individual mandate is scheduled to start early next year, when people start filing 2014 tax returns. As of late April, 77,000 families and individuals had requested an exemption from to the mandate — and the federal government hadn't rejected any.