Yellow is fake gold; it's veneer and show rather than substance. We see that with the yellow cocktail music at Gatsby's party (1) and the two girls in twin yellow dresses who aren't as alluring as the golden Jordan (3.15).
I think a moderate income is income above the median for famlies in your county, but not more than 25% of the median income. The IRS usually has this info for free, but I see they are now charging $10 for this on their web site for more recent years. http://www.irs.gov/taxstats/indtaxst...=96947,00.html.
The Survey of Personal Incomes (SPI) is a dataset from HM Revenue and Customs (HMRC) based on individuals who could be liable to tax. HMRC does not hold information on individuals whose income is below the personal allowance (Â£8,105 in 2012/13).