By calculating 50% and 90% ellipses - the ellipses that include 50% and 90% of urban development - we can measure compactness vs. dispersion of development. The more urbanized the ellipse, and the higher its density, the more compact the development.

Orange and Riverside Counties: 1972 and 1996

On these images the 50% ellipses contain 50% of the developed land area in each county. The indicated percentages, by contrast, indicate the percent of the area of the 50% ellipse that is actually developed. Thus a 77% ratio indicates that 77% of the 50% urbanization ellipse for a particular county is developed instead of open.