The graph below shows the representation of active-duty Army recruits for 2004 according to the median household income of their ZIP code. (Data are not available for the individual recruits' median household income.) Each bar represents the ratio of two proportions: the share of total recruits living in ZIP code areas whose median household income falls within the range over the share of the total youth population living in such ZIP codes. A score of more than one means the income range is over-represented. A score of less than one means the range is under-represented. Note that the peak of the bars falls in the range of $30,000 to $59,999. In other words, neighborhoods with low to middle median household incomes are over-represented. Neighborhoods with high median household incomes are under-represented. (The comparable median household income for the U.S. is $47,837.)

Notes: Median household income estimates by ZIP code are drawn from 2005 estimates from Claritas, Inc [1] . (These data were purchased by NPP.) Though the Army data are for FY2004, Claritas did not make estimates by ZIP code for 2004, nor did any other major demographic company or government agency. Army data were obtained from the Army through FOIA requests submitted by Peacework Magazine. The graph includes data for 63,039 recruits. Recruits from Puerto Rico and U.S. territories are not included. Recruits which came from ZIP codes with median household incomes of zero, or less than $5,000, were supressed since that effectively means we have incomplete data on the ZIP codes in which they live. Fewer than 2% of recruits were excluded. NPP had previously released a similar chart with over-representation showing in a slightly lower range. That chart, however, included Army Reserves, and was based on 1999 Census data, whereas, this chart is based on median household income projections from Claritas closer to the year of the recruiting data.
Links:
[1] http://www.claritas.com/claritas/Default.jsp