One of the signature promises by Donald Trump during the 2016 presidential campaign was to bring back the country's manufacturing sector.

As president, Trump has enacted pro-business policies, including a cut to the corporate tax rate, rollbacks of business regulations and an aggressive posture against trading partners such as China that have spent decades competing against U.S. factories.

But despite Trump's aggressive pro-business agenda, the results on his watch have been mediocre for the manufacturing sector, even before the coronavirus pandemic drove the U.S. economy into its first recession in a decade.

Here's a chart showing manufacturing employment by month. The blue portion shows the period under President Barack Obama, while the red shows the period under Trump.

Manufacturing employment did increase from mid 2017 to early 2019, but at roughly the same pace as it did for most of Obama's tenure. And for the year between early 2019 and early 2020, manufacturing employment stagnated. And that was before the coronavirus hit; during that yearlong stagnation, the economy was still expanding overall.

"There was nothing special or extraordinary about Trump's two years of manufacturing job growth, other than to say he benefited from synchronized global growth, which is very rare, and juice from the corporate tax cut, which probably shifted investment and hiring forward a bit," said Scott Paul, president of the Alliance for American Manufacturing, which has applauded many of Trump's goals on manufacturing policy.

Here's another way to look at the sector during Trump's tenure: gross manufacturing output by quarter.

By this metric, too, output rose during the first year and a half of Trump's presidency, though not much faster than during most of Obama's presidency. And since then, output has stagnated or declined slightly.

Finally, wages for rank-and-file workers in manufacturing didn't improve much either, as measured by average hourly earnings of production and non-supervisory employees.

Under Trump, hourly earnings for manufacturing workers continued rising much as they did under Obama, and they didn't gain ground on earnings for private-sector workers as a whole.

Meanwhile, the nation's balance of trade in goods — a measure of manufacturing exports vs. imports — initially got worse under Trump before improving to roughly where it was when he took office. "Prior to the pandemic, we were seeing increases of imports from Vietnam, other Asian economies and Mexico," Paul said. And any recent manufacturing gains were wiped out by the COVID-19 lockdown, observers say.

All told, Trump tried to boost manufacturing, but significant improvements weren't showing up in the data even before the pandemic hit. We rate this a Promise Broken.