I know I pull too much from the Wall Street Journal, but I just can't not share this beautifully phrased paragraph that distills current political streams and what they could mean for the continuing integration of markets and labor across international borders. 

Think here about the expansion of export markets for California produce and our continuing need for people to do the work of agriculture, many of whom come from outside of the US.

"But the economic benefits of integration must be weighed against the political loss of sovereignty.  You could almost certainly integrate the entire world economically and achieve massive economies of scale and integration.  Efficiencies in product, service and labor markets would improve productivity and generate higher overall income levels.  But most people in the world wouldn't tolerate the political implications, including free mass integration and steady erosion of cultural identities through universally applied regulations."  - Gerard Baker, "The Great Brexit Breakdown", Wall Street Journal, Dec 8, 2018.

My take? If one views the current political state of many of the world's well developed and internationally integrated economies through the lens of the preceding paragraph, a lot of what is happening right now makes sense.  With this in mind, the question which follows then would be are we at this time striking the political upper limit to the integration of markets and labor across international borders?