In his first interview since being confirmed, Treasury Secretary Steve Mnuchin told CNBC that the Trump administration will apply dynamic scoring to its budget, and that the combination of tax cuts and regulatory rollbacks will spur 3 percent growth by the end of 2018.

Dynamic scoring, as opposed to the static scoring the CBO uses to calculate growth projections, accounts for presumed economic activity. The non-partisan CBO is projecting 2.3 percent growth for 2017, and an average of 1.9 percent over the next decade.

Basing White House budget proposals on economic assumptions is a longstanding practice, says Marc Goldwein, senior vice president and policy director at the Committee for a Responsible Federal Budget, a non-partisan think tank that advocates for fiscal discipline.

"It's a reasonable way to score a budget, but where dynamic scoring becomes problematic is when a growth rate is set first," said Goldwein.

The 3 percent growth projected by Sec. Mnuchin will be "incredibly difficult, but not impossible" to achieve, thinks Goldwein. And a 4 percent rate of growth will be nearly impossible, he says.

In order to hit 3 percent growth by next year, the labor force would need to generate record productivity levels, according to CRFB's analysis.

"There is no reason to think that even a smart mix of tax reform, health care reform, and regulatory reform will be enough to guarantee 3 percent growth," said Goldwein. "We should aspire for that rate, but to count on it or assume it would be a little ridiculous."

In its simplest terms, the labor force's productivity rate is measured by dividing total GDP by the number of hours worked.

Today, the country's productivity growth rate is below 1 percent. The CBO is projecting that to improve. But in order to achieve 3 percent growth, Goldwein and the CRFB say the economy's productively rate will have to increase by 2.2 percent over a sustained period. And in order to achieve 4 percent growth in GDP, productivity would have to grow by 3.2 percent.

"There is no precedent for that level of productivity growth," said Goldwein. The last time productivity levels averaged 2 percent was in the late 1960s.

Productivity growth has remained below 1 percent since the financial crisis. Demographic headwinds from baby boomers leaving the workforce have contributed to lackluster productivity. And while millennials now account for the largest segment of the work force, they are far from hitting their peak earning potential.

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As more boomers continue to retire or partially retire, economic growth will be even more dependent on improvement in the labor force's productivity, according to the CRFB.

The White House is expected to release a so-called skinny budget, which accounts for the limited time the Office of Management and Budget will have to prepare a proposal.

That will give the Trump administration some latitude in its accounting, as much of its policies will still be in development.

But CRFB nonetheless cautions against the accounting "gimmicks" or "budgetary sleights of hand" that past administrations have used to hide the cost of spending and exaggerate savings in order to rationalize policy proposals.

"Using such deception to make the budget look fiscally responsible would signal that the Administration is not serious about dealing with the debt," according to a paper released by the Goldwein and the CRFB.

CBO says the country's debt is $14 trillion, or about 77 percent of GDP. Under its long-term projections, total debt will hit 145 percent of GDP by 2047.

The good news for the Trump administration is that even micro improvements in growth will reduce debt levels.

A 0.1 percentage point increase in GDP would reduce the debt by $300 billion over the next decade, according to CRFB's figures.

But the lavish growth projections often proclaimed by Trump, and even the tempered 3 percent projection of Sec. Mnuchin, should be viewed by the public as aspirational, and "have no place in any official government projection," according to CRFB's analysis.