Not helping: I think they've done an exceptionally poor job of clarifying how they defined the metropolitan areas. For example, the label for the data in the Boston area (lifted off the map, which was the only place I could find the slightest mention) is "Boston-Cambridge-Quincy, MA-NH". Grouping MA and NH?! Conversely, Riverside and Los Angeles are separated despite covering a similar geographic range. I'd love to see the geographic regions in this study shown as polygons on a map, along with some sense of the total population per region.