In fact, the sequester was never intended to go into effect. The mere threat that it might was supposed to prod lawmakers to find a smarter, more gradual way to reduce deficits.

But Democrats and Republicans still can't agree on how, despite knowing this day would come for over a year.

House Republicans have proposed replacing the defense cuts with more nondefense reductions. Senate Democrats want to replace all the cuts with a mix of targeted spending cuts and tax increases. Each side rejects the other's solution.

How much will the sequester reduce deficits? Between now and 2023, projected spending would be reduced by more than $1 trillion if the sequester plus related spending caps in subsequent years are left in place, according to Congressional Budget Office estimates.

Will the sequester hurt the economy?

Yes, if it stays in effect for the rest of the calendar year.

The CBO estimates that it could reduce economic growth by at least 0.6 percentage points and reduce job growth by 750,000 jobs.

Coupled with this year's payroll tax cut expiration and the higher tax rates on high-income households, the CBO estimates growth will be curtailed by a total of 1.5 percentage points.