The link YATA1's been posting actually does [0]. About 3.46 percent of people enlisting come from households making more than $100K, although those households make up about 8 percent of the population [1]. In general, it looks like it matches the population more than the quintile breakdowns do.

[0]: On page 6: http://s3.amazonaws.com/thf_media/2008/pdf/cda08-05.pdf#page... [1]: https://www.census.gov/data/tables/2007/demo/cps/hinc-06.htm...