This map, of which my Southwest LRT map is a compliment, shows the average jobs-plus-population density per acre across Hennepin County, MN. Areas that are shaded have at least 5 jobs+pouplation per acre. It was created in ArcMap by taking 2010 Census population data at the Census block level, plus 2011 jobs data available from the US Census (also at the block level), and averaging out the numbers on a per-acre basis.
Several studies over the past four decades (dating back to a 1977 study by Boris Pushkarev and Jeffery Zupan) have found at least an indirect relationship between job density, population density, and transit ridership and effectiveness. The studies have generally found that an average density of 5 jobs/population per acre is enough to support basic bus service, with higher levels of density able to support higher levels of transit service.
Here, we see the densest areas of Hennepin County are downtown, the U of M area, and parts of the Phillips neighborhood and Ventura Village. Except for isolated pockets, most of the county west of I-494 and north of 610 has a density of less than 5 per acre.