For those occupations where there is not an hourly mean wage published, the annual wage has been directly calculated from the reported survey data.

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For our lists, we excluded those occupations where total employment was less than 25, 000.

FORBES: America's Top 20 Growing And Disappearing Jobs

So while huge differences in productivity exist in many occupations, this is especially true for those involving the application of knowledge.

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The number of jobs for engineers, technicians, scientists and those in the computer and math occupations grew by 19.5% from 2001 to 2013 in the D.

WSJ: Washington, D.C.: The New Boomtown