Every source I can find (2014-2018 data from a variety of places) puts it between 97th and just over 98th; probably hasn't changed more than a couple of points since.
> I do not know what upper middle class is supposed to mean. Does it mean 90-95 percentile?
If by “middle class” one means petit bourgeoisie, then 95th to 99.something percentile for the upper range of that class is fairly reasonable; the haut bourgeoisie are a very narrow slice, and economic classes in that classic sense have overlapping income ranges, because they are more about how one relates to the economy than income level, though the two are correlated.
OTOH, the language of economic class these days is used in many murky and inconsistent ways.
EDIT: Just to be clear, the classic idea of the petit bourgeoisie as the middle economic class of capitalist societies does not mean that they represent the average or some range around the average; the working class makes up the vast majority, the haut bourgeoisie (the class of major capitalists) is a tiny slice that controls most of the wealth, and the petit bourgeoisie are a fairly thin (though much broader than the haut bourgeoisie), largely relatively rich class that is “middle” in the sense of deriving income from a mix including both a substantial contribution from personal labor (the predominant support for the working class) and a substantial contribution from personal capital (the predominant support for the haut bourgeoisie)—the classic example of that mix being the independent small business owner whose labor is applied to their own capital rather than either being rented out to some capitalist, or gaining returns on capital by renting others labor to apply to it.
Anyways, I think the answer is just based on how you want to define middle and upper class.
It all sort of feels relative. If a “beginner” single family bungalow costs 850k+ in my neighborhood, home ownership still feels like a gamble (well, the accompanying debt burden would make me uncomfortable). A $4k mortgage payment does not sound fun if I were to lose my job, for example.
Even if you’re making 500k a year, depending on the part of the country, it may take a fair few years before you make that jump.
I think it’s the difference between having _wealth_ and having a lot of disposable income. There’s a fairly big difference. You can convert the latter to the former but not everyone does.
The cost of maintaining your Upper Middle Class status is very high: tuition for elite, private schools, mortgages on giant homes and vacation homes, leases on luxury cars to keep up with the neighbors, and the desire to live in high-cost exclusive communities, etc.
Because of all of the above, people that should be "rich" if you look at where they are on an income distribution graph, actually do not feel "rich." So they identify as Upper Middle Class.