Not necessarily. Undocumented doesn’t mean “excluded from the stats”, it means “doesn’t have a valid work visa or social security number”.

I’m not sure if something similar happens in construction, but I’ve heard that in the landscaping business a supervisor will just pull up to a Home Depot with a pickup truck, and there’ll be a bunch of people waiting around, and they’ll go “Who wants $X for Y hours?” And then 4 or 5 guys get in the back of the truck and they head to the work site.

In a situation like that, you’re probably keeping track of how many people you employ each day so you can figure out how many you need for future projects, but you’re not gonna be able to produce a list of social security numbers if someone asked.