How to estimate income level / ethnic ratio from your traffic

Use this API to get demographic data:

http://www.census.gov/data/developers/data-sets.html

For each visit to your site, convert ip to zip code by maxmind; use zip code to retireve income level / ethnic ratios by the census API. Sum the ratios by proportion - the result is the estimated income level / ethnic of your traffic (assuming people in a zip visit your site at random).