We're looking at new ways to segment our database to target appeals at donors, especially related to planned giving. One data source that seems like a good option is to match US donors' zip codes to average incomes in that area. There can be a high margin of error with data sets like this, but it is also publicly available on the US census website.

Here is a link to download the most recent data set I or our consultants can find (from 2017):
https://data.census.gov/cedsci/table?q=Median%20Household%20Income%20in%20the%20United%20States&hidePreview=true&table=S1901&tid=ACSST5Y2017.S1901&t=Income%20%28Households,%20Families,%20Individuals%29&g=0100000US,.860000&vintage=2017&layer=zcta5&cid=S1901_C01_001E&lastDisplayedRow=0&tm=false

It seems like the data is updated inconsistently and not quite annually, so we'd need to decide how often we try to update it. Is it worth exploring if we can add this to Civi, or use it to put donors into certain groups?