The French trade minister’s call on Tuesday for an end to trade negotiations between the European Union and the U.S. is only the latest evidence that it’s becoming increasingly difficult to remove barriers to world trade.

The comment by Matthias Fekl to end discussions over the Transatlantic Trade and Investment Partnership come after Germany’s vice chancellor over the weekend said the talks have failed. And it comes as the Trans-Pacific Partnership awaits congressional approval amid attacks from both major presidential candidates. Sen. Majority Leader Mitch McConnell told a local newspaper that the upper chamber won’t vote on TPP this year because of “serious flaws” in the agreement.

Citi Research analyzed recent data on world trade this month in a note to clients. Using data from Global Trade Alert, they have found a rise in protection measures among Group of 20 countries since the financial crisis.

Whether coincidental or not, trade growth has stalled, particularly for goods. That’s also seen in the rapid drop in port activity, particularly out west in ports that focus on trans-Pacific trade.

The economists at Citi acknowledge that studies often show small effects on trade from protectionist activities. That said, they said the rise of protectionism and the persistent weakness in world trade growth is a major threat to global growth and investment.

And, they add, the slow trade growth is both cause and effect of the productivity growth. One point the Citi economists make is that productivity growth is not just slowing in the U.S. but for all the major industrialized nations.

Trade policy has traditionally been part of the discussion for improving productivity growth. But now, that discussion is focused more on infrastructure investment or monetary policy.

“In a world with low productivity growth, significant policy and political uncertainty, it is difficult to envisage an acceleration in investment growth. This is one of the challenges we expect to constrain policy makers’ actions in the quarters to come,” the Citi economists say.