In the final presidential debate, Donald Trump made a bold promise to raise gross domestic product (GDP) growth rates: "we're bringing it from 1% up to 4%, and I actually think we can go higher than 4%. I think you can go to 5% or 6%."

While the stock market soared under the Obama administration and the headline unemployment rate has plummeted, economic growth has remained subdued. GDP, the most commonly cited measure of an economy's total output, has not hit 3% annual growth since 2005, a far cry from the 4%, 5% and 6% rates seen in much of the last century. (See also, Obama's Economic Legacy in 8 Charts.)

Despite his boss' enthusiasm, Treasury Secretary Steve Mnuchin appears to be erring on the side of caution. He has repeated a target growth rate of 3% several times over the past few days, telling Congress on Thursday that this rate is "very achievable." The next day he took a question regarding the 3% target on CNBC's Squawk Box, saying the economy could begin seeing that growth rate "towards the end of the year." On Sunday he told Fox News, "this is all about creating growth, and we're going to get back to a 3% GDP or higher."

It is not clear whether Trump has endorsed the more modest target; a 1 percentage-point difference in output, using fourth-quarter 2016 data, amounts to around $188.6 billion. The president will address a joint session of Congress on Tuesday and is expected to send a fiscal 2018 budget proposal to executive agencies Monday. Details of this budget have begun to emerge, including a $54 billion increase in defense spending to be financed by cuts at the State Department and elsewhere.

Trump's plan to boost growth hinges on a combination of cutting taxes, increasing infrastructure spending, overhauling trade policy and limiting immigration. Independent observers have expressed varying degrees of enthusiasm for these plans. In June, Moody's forecast that Trump's platform, implemented "at face value," would push annual growth down from their 2.3% baseline to a 0.6% annual average for the period from 2016 to 2020. On the slightly more optimistic side, the Tax Foundation forecast in September that Trump would add a cumulative 6.9% to 8.2% to GDP over the unspecified long term, over and above the 19.2% the Congressional Budget Office estimated for 2016 to 2025 (in other words, the Tax Foundation expects something on the order of 2.7% per year).

The Federal Reserve predicts long-run growth of 1.8%, while the nonpartisan Congressional Budget Office forecasts 1.9% annual growth from 2021 to 2027.

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