A Government Accountability Office (GAO) report concluded that analyzing the relationship between military pay and pay of private sector employees presents challenges and limitations that often prevent direct and meaningful comparisons.  Military and private sector pay are difficult to relate, according to GAO, because of the unique working conditions of military personnel and the difficulty in quantifying special benefits they receive.  In addition, the report states that data limitations and the inability to match up truly comparable occupations do not allow exact comparisons.  GAO points out that various studies by the Congressional Budget Office (CBO), the Rand Corporation, and CNA Corporation, and the Congressional Research Service (CRS) have struggled with these problems and reached inconclusive results.  The report also noted that DoD faces unique recruiting and retention challenges, particularly the need to bring in, and then keep, people willing to make a long-term commitment.  These challenges require a greater emphasis on a wide array of benefits, as well as salary.  And although these benefits are often difficult to quantify, GAO urged DoD to continue to explore ways to develop values for these benefits to better asses the success of its recruiting program.  The GAO report was required under the National Defense Authorization Act for Fiscal Year 2010