A new map created by Harvard PhD student Robert Manduca plots all of the jobs across the United States, putting one dot on the map for each job that exists. The dots are all color-coded based on the sector each job belongs to. Blue is for professional services; green for healthcare, education, and government; yellow for retail, hospitality, and other services; and red for manufacturing and trade. The map uses US Census data from 2010, the latest available for Manduca's purposes. As he told CityLab, his visualization is useful because "jobs are more concentrated than people. It gets across how tightly packed they are in many U.S. cities."
In the Bay Area, of course, jobs spread down through Silicon Valley, but the tightest cluster—especially of professional services and healthcare, education, and government jobs—sits right in downtown San Francisco. On the city's western side, healthcare, education, and government dominate, while there are a few manufacturing and trade jobs hanging on at the southern edge of town.
Oakland also has a core of blue (professional) and green (healthcare, education, and government) sectors downtown, but further afield, manufacturing and trade jobs begin to abound, especially around the Oakland Airport and in the areas east and south of Hayward.
Silicon Valley is something of a mixed bag, with lots of professional-services jobs clustered around Palo Alto and Los Altos and a colorful mishmash of nearly every kind of employment, including big red manufacturing and trade hotspots, in North San Jose.
Because the data is from the 2010 census, it reflects Bay Area employment mid-recession. We'd be curious to see how legible the changes of the past five years would be on a map with this level of detail, though sadly we'll probably have to hold out at least until 2020 for that.