Now that's an interesting indicator - many of these are variations of the same theme and lagging indicators. Yours is (except for areas in immediate transitions) a real time indicator idea. At least in the US.

It would definitely work in the UK as well - especially as you can tell the age of a car from the number-plate. Find a run down area and track the number of newer family cars or BMWs/Audis.

Will not work in the USA, poor black people buy new German luxury cars and live in dumps. I don't understand.

So look for Teslas?

...or the fact that there are cars parked on the street vs not.

I've lived in poor suburban neighborhoods and generally, the poorer the neighborhood, the more cars were parked on the street. I've lived in neighborhoods that looked like used car lots! Poorer neighborhoods tend to have more houses without garages. And in neighborhoods that have garages, the poorer families tend to use their garages as extra bedrooms, workshops, meth labs, basically anything BUT storing cars.

Note, this stereotype probably only works in the suburbs, because in urban areas, every potential parking spot is filled with a car by default.