Good question. In some jurisdictions, an interest that becomes “too small” is quashed by administration of state law* and the interest is returned to the surface owner. Also, there is brisk trade in some areas from time to time, so tracking all of that would be a lot of work. Clearly, the number ebbs and flows with the market for the products.
I am looking for a snapshot. If I could state, with some authority to back me up, that circa 2010 there were X million owners, I might gain some traction in discussions on how to best preserve and promote private ownership of property.
- As an aside, I feel such laws are patently unfair, as most severed mineral interests were secured by an agreement between willing parties. I know there are exceptions, and real estate in general is rife with traps for the naive. Nevertheless, those laws smack of an unethical taking of property for the benefit of a few; the polar opposite of the intention of public domain policy.