After laying off roughly 2 million workers during the recession, the construction industry may not have enough crews to keep up with demand for building projects. Brennan Linsley/AP hide caption

itoggle caption Brennan Linsley/AP

Men sit by the side of the Panama Canal as a ship sails past in Gamboa near Panama City, last month. The expansion project is aimed at accommodating the world's largest container ships. Arnulfo Franco/AP hide caption

itoggle caption Arnulfo Franco/AP

A screengrab of a satellite image of Cordoba, Spain, in 2004 (left) and 2011. Satellite images via Google Earth and Nación Rotonda hide caption

itoggle caption Satellite images via Google Earth and Nación Rotonda