Economic land is any capital that has a fixed amount, that you can't make more of. When the local governments in the Bay Area started capping the amount of buildable square feet, they greatly accelerated inequality by converting regular living space and working space into economic land, just like the real land it sits upon.
This is why economic inequality skyrocketed so much. Rentierism resulted in so much being stolen from anybody who doesn't own the land, and blocks out so many people from even having access to the economic system.