The cliff also includes $110 billion in automatic spending cuts at the Pentagon and other federal agencies. The Tax Policy Center report only examines the effect of tax changes.
One striking conclusion of the study: Although the political debate has focused on the Bush tax cuts and whether they should be expired for high earners, the tax portion of the fiscal cliff is not monolithic. Instead, the Tax Policy Center identified nine categories of taxes, each with its own set of political considerations.
Researchers then ranked the changes according to the likelihood that they will take effect. Their conclusion: The payroll tax holiday will almost certainly be allowed to expire, decreasing the average worker's paycheck by about $80 a month.
However, analysts concluded, Congress is highly unlikely to let the alternative minimum tax expand to strike an additional 20 million families in April. Households making from $65,000 to $500,000 would take the hardest hit.
"That's something that's unlikely for Congress to want to embrace," Tax Policy Center director Donald Marron said at a morning briefing for reporters.