
While there is no established, traditional definition, I’m pretty comfortable with the one I invented (claiming no originality, but so far not finding it elsewhere):
the intersection of working class and capital class
I think it captures the underlying idea that a middle class person is somewhere between the two real classes (rulers/owners and subjects/workers) in a way that dovetails with democratic ideals: collective self-rule/governance and economic self-determination/independence.
Further explanation:
To fit this definition, you need to be wealthy enough to own real assets (like your home, a small business, a farm, etc.) but you can’t be so wealthy that you (and the rest of your household) don’t need to work (unless you’ve all reached retirement age). It’s still a loose definition – does owning a car count, is a house really yours with a mortgage, etc. and why doesn’t being able to afford renting an opulent apartment count – but that’s because to me it’s not about lifestyle or social status. It’s only partly about how well your needs are met. Power coupons have real influence, but money is still only a social construct – and worse it’s based on power taken from someone else. It can and will be manipulated by those who already have the most of it. But assets and especially land have intrinsic value based on utility that cannot be indirectly manipulated; when the price of land goes up, what’s really happening is the value of money going down.
I think the heart of the matter is, what is the nature of your stake/holdings within your own country? Do you have a form of power and agency that the political machinery must respect but does not revere? The numbers aren’t what matters and would necessarily vary wildly across the nation anyway. What matters is how vulnerable you are to the effects of wealth inequality. That vulnerability is what should be getting highlighted, and I think it captures what was on people’s minds back in the 90s as they talked about the middle class shrinking. It was not just wealth but power concentrating either on you or (far more likely) away from you.
In capitalism, capital is the only real power and politics only a moderating force. So the health of a democracy can be measured by the distribution of power – i.e. the size of the middle class. While you can live a good life in the lower class (which may be inescapable due to such things as being disabled), it’s by the grace of whomever holds power over you or the social systems that a majority (hopefully) dictates shall respect persons rather than property and ability. The lower class has no intrinsic power, so when middle class falls below majority
Below middle class, you are disenfranchised even if you still have a vote, because the economy sees you only as a burden and markets have no natural incentive to consider you. If you are lower class and the system hasn’t the grace to protect your interests and quality of life, that is the system’s failure. Above middle class you are privileged with the capacity to force economic changes others do not want, and on top of having a vote the political system will defer to you wherever you hold the capacity to help or harm – and ignore the voting power of your lesser opponents. That’s to say nothing of your ability to influence lower and even some middle class people to vote your interests instead of their own. If you are upper class and the system hasn’t the fortitude to both constrain and redistribute your power, that is the systemic failure that most erodes middle class power. Once middle class no longer holds the majority of power, capitalism spirals into “late stage” and steadily grows the lower class while undermining their supports.
Middle class is where fair equity lies, by virtue of resilience against the abuses of wealth inequality. And yet though it should be as big as possible, middle class is the only one that can definitely be entirely empty.
I think most might be overstating it. Maybe it isn’t in the forefront of most people’s minds, but that’s a reflection of who dictates what gets traction in public discourse. I’d wager most people over 40 who aren’t zealous conservatives have figured it out.