Keystone Research Center announced the findings of a study by the Iowa Policy Project. The press release explained the rationale behind the research:

The two think tanks undertook an analysis of manufacturing jobs in the wake of debate about the overall “jobs score” under Republican and Democratic presidents spurred by former President Bill Clinton’s speech to the Democratic National Convention. Manufacturing jobs have particular significance because they pay better to equivalent groups of workers than jobs in other sectors. Manufacturing also leverages more related employment (up and down the supply chain and in consumer industries) and more export growth than other sectors.

Think Progress highlights some of the findings:

Democratic presidents presided over estimated employment rise of 7 million in the manufacturing sector over the course of seven administrations; In nine administrations, Republicans saw a fall of manufacturing jobs by an estimated 9 million.

The press release contains more detailed findings.