This geospatial data shows both the shape of the census units or counties as polygons, and the color represents the number associated. In aggregate you can quickly get a picture of meaningful information. When you turn on other layers in Google Earth the data can be better understood. For example, my daughter was asking why the population density was so low (black) in the western part of North Carolina. I turned on the Parks and Recreation layer and you could immediately see why no one was living in that area. In fact, you could see other areas around the state which were parks and therefore had low or zero population density. You can turn on the Roads layer, and the Populated Places layer to understand the geographic references to the data better. There are many other layers to explore in relation as well. This is great stuff!

Check out Juice Analytics' Absolutely Google Earth which is a collection of useful links for serious Google Earth users. You can find some of these links in Google Earth Blog's Reference Links Page. Saw this first via OgleEarth. Digg it!