If somebody produces more than they cost to hire, they are productive.
There are two ways to increase net productivity, you either produce more on a gross scale, or you lower your cost (wage).
If a Mexican comes in and is willing to produce $10/hr worth of food but he only costs $5/hr, that Mexican is more productive than a white man who can produce $30/hr of food but demands $25/hr. On one hand, for every dollar you throw at them you get $2/back, whereas with the whiteman you only get $1.2 for every $1 you chuck at them.
Cheap labor is what yields productivity. Automation is useful when and only when it becomes more productive than labor, which is when the cost of labor becomes too expense to justify choosing it over automation, or when automations's gross productivity rises so much that its output/input ratio exceeds that of labor.
Immigration is Objectively Good for the Economy
