I'd say the criteria is ownership. The latter two of your examples are owners by definition, and the managerial class are usually owners through large stock options.

Employees are sometimes owners through stock purchase plans, but here I'm identifying management as that elite whose merely lucrative salaries are dwarfed by multi-hundred-million stock grants. CxOs and their immediate lieutenants, generally. The people notorious for now earning more than 400x the annual income of their employees, up from a factor of about 35 around 1980.

It's helpful in understanding the modern era to refer back to feudal systems. The pinnacle of society is the wealthy aristocracy, served by a second layer of loyal retainers who are handsomely rewarded and may even ascend themselves into the aristocracy. Substitute the terms "owners" and "managers", and you're back in the 21st century.

I hope I'm not saying anything you haven't heard recently. Thomas Piketty's "Capital in the 21st Century" laid out the structure of economic inequality with scientific precision, proving, in layman's terms, that without some government regulation (crucially, an inheritance tax), it really is true that the rich get richer and the poor get poorer. Someday Piketty's expression "r > g" may be as recognizable as "e=mc2". We've already managed to revert to the economic regime of the 1920s, and if nothing changes, get ready to say hello to the 18th century.

Ya know, when Bernie Sanders announced he's running for President, I went to his web site to read up on his positions. A minute later I said to myself "holy shit! I'm a socialist!" and sent Bernie $50. What he prescribes is the only way out of the mess that conservative economics has gotten us into.