Using income as a global measure is a favourite trotted out by hair-shirt progressives, too. To be clear, I don’t think you are one of those or a Libertarian greedhead. Like me, you’re just an affluent Westerner who’s smart about sustainable economics and honest about where he stands economically and what he can do to make things better for everyone.
Income is a symbol of global privilege and remains so when you take into account disparate cost-of-living figures. That’s especially true of the steady income that comes with a career, given how a greater and greater proportion of the U.S. workforce becomes more precarious if not unnecessary with ever passing month.
However, that changes when one’s assets are enough to provide a comfortable income without having to do any work (this is where Piketty and his “r > g” formula comes in on a microeconomic scale). If one has $1.5 million in invested assets (as opposed to a fully paid off home worth $1.5 million), that amounts to approx. $60k/annum in income without lifting a finger. If one is in that situation and still of working age and inclination, one is probably also gaining a nice income from a fulfilling career on top of that thanks to a combination of social and financial capital.
When we use the term “the 1%” we’re talking about having both the lifestyle and the financial security of an rich person. The former can be faked thanks to consumer credit or easy-term mortgages, but those bills eventually come due for non-1%ers in a way they never do for members of the 1% if they avail themselves of such credit. That, and the greater difficulty that bad actors have in spinning it their way, is why assets remain the better measure for distinguishing the truly wealthy from everyone else on a global or domestic scale.