Lots of medical jobs - the NIH is in Bethesda, and Johns Hopkins Hospital is the #1 employer in Baltimore (with the university not far behind). Plus tons of NASA (Goddard), DoD (Ft. Meade and NSA headquarters), and related contractors in the DC suburbs. DC has more post-graduate degrees per capita than any state (and more than most cities), and Maryland gets a lot of spillover.<p>The difference in the statistics is explained below the chart - &quot;STEM concentration&quot; is based on employment field, regardless of education.