Lot of illegals working for cash that is not reported. Go to any truck dock in an urban area, there are ATM’s available on the dock to pay “lumpers” in cash to unload your truck. Big companies are looking the other way at the lumper practice so they don’t have to hire full time workers.
Here’s another example. Watch any of the home improvement or rehab project TV shows that are shot in the U.S. (HGTV, e.g.). You will see they film them so they never show the workers’ faces or sometimes they even get blurred out. It’s because all the construction workers they use are illegals.