Population Trends and Forecasts

Population Change Maps 1990-2000

Population Growth Patterns

The gross change in number of residents per census block was calculated by combining GeoLytics' "1990 Long Form in 2000 Boundaries" census data with the "2000 Blocks." With this combination we were able to calculate the change in population by 2000 census block group boundary. This data was then symbolized on a map so that red colors indicate block groups with population growth, green colors indicate population decreases, and grey indicate either no change or an undefined change (outside of the study area or in a water body). The positive and negative growth categories were further broken down into four classes based on the magnitude of the change. More intense reds or greens indicate a greater magnitude of change. The dividing points between categories were selected for visual efficacy. The number of blocks in each of these categories was also calculated and is presented within the legend.

Household Growth Patterns

As we calculated the change in number of people by block group, the same calculation was performed using the 1990 and 2000 census figures for total households. Instead of displaying by the total number of households, the dataset was visualized by calculating the total rate of growth in households for all counties overlapping the Sacramento River Watershed. The percent growth for households for the region equals 17.5%. Blocks with negative growth in households are symbolized with a tan color. A light red indicates a positive growth rate, but one lower than the regional average. Dark red indicates growth greater than the regional average. A purple block group is one where the 1990 household count equaled zero (creating an infinite rate of growth).

Resources Used for Analytical Purposes

All of the demographics for both maps is produced from the CensusCD products produced by GeoLytics, Inc (GeoLytics, 2001, 2004). Because census block and block group boundaries changed frequently through subdivision, between 1990 and 2000, drawing a direct connection between the 1990 and 2000 census data can be challenging. Because of this, we intentionally kept the analysis straightforward. Other datasets used in the creation of these maps included a watershed boundary for the Sacramento River produced by the Department of Water Resources in 1999 as a component of the CalWater2.2.1 dataset (California Interagency Watershed Mapping Committee, 1999) and County Boundaries for California (Fire and Resource Assessment Program, 1997). A preexisting hillshade based on a 30m resolution digital elevation model (DEM) from the US Geological Survey provided a background for visualization only.

  • California Interagency Watershed Mapping Committee. (1999). CalWater 2.2.1. Retrieved November 2007, from http://gis.ca.gov/meta.epl?oid=22175.
  • Fire and Resource Assessment Program. (1997). California County Boundaries (1:24,000). Retrieved November 2007, from http://gis.ca.gov/meta.epl?oid=21384.
  • GeoLytics. (2001). CensusCD: 2000 Blocks. East Brunswick, NJ: Geolytics, Inc.
  • GeoLytics. (2004). Census CD: 1990 Long Form in 2000 Boundaries. East Brunswick, NJ: Geolytics, Inc.