President Donald Trump took to Twitter on Saturday to repeat what former Republican presidential candidate Herman Cain said on Fox regarding the deficit during his administration.

“The media has not reported that the National Debt in my first month went down by $12 billion,” he wrote, comparing it to a $200 billion increase in President Obama’s first month.

Most of the discussion about Trump’s comment Saturday centered on the inspiration for the president’s comment. (Cain had made similar comments earlier in the morning on television.) But it’s worth delving into the details themselves to understand why the president shouldn’t get credit for the turnaround.

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First, the obvious point: Trump had zero role in the federal government’s tax and spending decisions for January.

The people most involved were House Speaker Paul Ryan and Senate Democrat Patty Murray, who hammered out the fiscal 2014 budget deal whose framework is largely reflected today. Other key players included President Barack Obama and Senate Majority Leader Mitch McConnell. The government is operating under a bill passed in December, which expires in April.

The biggest reason the deficit is so different now, however, is the economic situation.

Obama entered office during the worst recession since the Great Depression, which not only depresses tax revenue but exacerbates spending — consider, for example, unemployment insurance. Trump entered office in a far different economic environment, one shaped in part by the policies of Obama and the Republican Congress.

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But what about the new confidence of businesses and consumers since Trump took office? There’s so far little evidence that the confidence has translated into actual activity.

Still, let’s be charitable and give Trump credit anyway. The Institute for Supply Management said its manufacturing index in January was consistent with 4% GDP growth and its services index was consistent with 2.9% growth. In October, those numbers were 2.8% and 2.3%, respectively.

So, averaging it out, let’s just say GDP growth is 3.5% — economists say it’s more like 2.4% — and Trump is worth a full point.

Receipts — that is, taxes collected from individuals and companies — were $344 billion in January.

That extra 1% translates to $3.4 billion. That isn’t nothing, but it probably isn’t real, and it isn’t commensurate with the $212 billion swing claimed by Trump.