The return of the border walls.

Since the early 2000s, border walls and fences have proliferated and become a global phenomenon with about a third of the countries having at least one wall or fence along its borders. Taking proper account for endogeneity, phasing-in effects and reverse causality, our gravity model for the years 1990–2017 (118 countries) finds a stronger trade-reducing impact of physical border protection structures ranging from 59% to 72%. This impact of physical border protection measures is non-monotonic: the immediate walls effect is insignificant but over the first 4 years after the creation of a wall, it starts to slash trade flows strongly and significantly. [ABSTRACT FROM AUTHOR]