If you look at the Bureau of Labor and Statistics they will happily provide you with more detail, for instance the median salary in a field for the top 10% of employees versus the top 90%.
I don't know how you'd keep that updated though, you can hardly say "the amount the richest 10% spend is the rich CPI" because it's a silly statistic. I don't know how you can reasonably say "the minimum amount required to be rich", it just seems silly on its face.
No, I don't think there's much of a way to make it work. It's probably more directly useful to understand whether people are saving money or how much debt they have, though that's going to lag.
I mean, or just ask people. The government is fairly good at doing that.
For income once again you can turn to IRS tax return data. I believe IRS can also sum your accounts as well as review transaction history. Creditors also report debts to IRS.
All told I believe the federal government can access all the information needed to know exactly what almost every American is paying for housing, how much they are being paid, how much they are spending, and how much debt they have.
