Issues in depicting population change with dot maps

Creating dot maps to show changes in racial and Hispanic population distributions between two census periods can be an effective way to examine one of the most important dimensions of change within any metropolitan area. Using dots of one color to show population increase and dots of a second color to show population decrease vividly reveals where changes have occurred within a larger total population. We prepared such maps for the book “Changing Faces, Changing Places: Mapping Southern Californians,” the text of which analyzes and interprets the population shifts evident on the maps. The maps show the expansion and contraction of racial and Hispanic populations in specific neighborhoods so that community leaders and residents alike can easily relate general trends to their localities. In this article we describe the preparation of these dot maps and explain major problems encountered in linking the 1990 and 2000 census population counts at the tract level. We explain our solutions, which we believe made possible more accurate mapping of neighborhood change.