Productivity levels per worker in Ireland two years ago were 40% higher than in Northern Ireland, a new analysis has found.

That compares to 20 years earlier, when productivity levels were more or less the same.

It follows two decades where productivity levels in the Republic have risen slightly, while in Northern Ireland they have fallen.

The findings are contained in first-of-its-kind new research produced by the Economic and Social Research Institute (ESRI) in partnership with the Department of the Taoiseach's Shared Island initiative.

The paper found that in Ireland, as education and investment increases, so too does productivity, while export intensity is also important.

"The usual factors…were found to be important determinants of Irish productivity," said Adele Bergin, one of the report's authors.

"However, no significant relationship is found between these factors and Northern Irish productivity."

"It may be the case that there are other factors that need to be considered in devising a policy response."

The report said it is possible that the impacts of The Troubles, a relatively closed economy in terms of international trade, peripherality, limited results from regional policy and a historical reliance on public sector employment have all combined to subdue the impact of market forces among Northern Ireland firms.

This, it suggested, could have led to a productivity trend that appears to be largely influenced by outside factors, rather than key policies.

Of 17 sectors in both jurisdictions, productivity levels in the south were markedly higher than in the same segments in the north, the analysis found.

In Northern Ireland productivity levels were higher in electricity and gas supply as well as construction.

But productivity levels in Ireland were considerably greater in administrative and support services, financial and insurance, legal and accounting and scientific research and development.

The study said a rapid expansion in investment and improvement of skills is needed in Northern Ireland, with post-secondary level a particular focus.

But the authors also found that unless there is a comprehensive strategy that aims to boost competitiveness among Northern Ireland based businesses, such reforms on their own are not guaranteed to improve productivity in the north.