Just how big is the payroll tax cut?

The payroll tax cut extension will save workers a total of $114 billion this year. That means an average cut of $714 per worker, though some will take home more (and some less).

The 2-percentage-point payroll tax cut extended by Congress in December and again last week will save workers a total of $114 billion this year, according to the Joint Committee on Taxation. Spread over nearly 160 million workers, that’s an average tax cut of $714. Yet the typical news report says “the average worker earning $50,000 [will] take home an extra $1,000.”

That’s a big difference. What’s going on?

The calculation implicit in the news report is simple arithmetic—2 percent of $50,000 is $1,000. But the average worker earns much less—just under $40,000 in 2010, according to the Social Security Administration. That suggests that the average tax saving would be about $800, still more than $714.

The remaining difference results from the Social Security tax cap–$110,100 this year. Since incomes over the cap go into the overall wage average, the average wage subject to the Social Security tax is less than the average for all pay, roughly 10 percent less.

But TPC estimates that the average tax reduction will total $921, well above the average worker’s savings. That’s because TPC looks at tax units—individuals or couples who file tax returns (or would if their incomes were high enough). And TPC leaves out dependents and hence misses the tax savings for many younger workers. Tax units are similar to both families and households but not the same as either.

So here’s the bottom line (or lines):

1. Nearly 160 million workers will take home an average of $714 more during 2012.
2. About 122 million tax units will save an average of $924 in payroll taxes.

Only above-average workers will get the $1,000 repeatedly promised in the media.