DRAFT RURAL-URBAN POPULATION CHANGE IN PUERTO RICO, 1990 TO 2000 Mei-Ling Freeman Geographic Standards and Criteria Branch Geography Division US Census Bureau For presentation at the Western Regional Science Association annual meeting, Santa Fe, NM, February 22-25, 2006. This paper reports the results of work undertaken by the U.S. Census Bureau staff. This report is released to inform interested parties of research and to encourage discussion. 1
Rural-Urban Population Change in Puerto Rico, 1990 to 2000 Introduction According to published data from the 1990 and 2000 decennial censuses, Puerto Rico s rural population decreased sharply from approximately 1 million people (29 percent of total) in 1990, to only 213,000 people (6 percent of total) in 2000 (Chart 1, Map 1). The urban population, on the other hand, increased from 71 percent of total population in 1990 (2.5 million people), to 94 percent in 2000, or 3.6 million people. Percent of Total 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Chart 1: Percent of Total Urban/Rural Population 1990-2000 71% 94% Total Urban Source: U.S. Census Bureau Urban/Rural 29% 6% Total Rural 1990 2000 Population growth in general certainly explains part of the increase in urban population, but it does not appear to be the major reason behind the substantial increase in urban population in Puerto Rico in 2000. As Table 1 illustrates, there was not a substantial population growth between 1990 and 2000, compared to previous decades. Although the total population increased steadily between 1960 and 2000, population growth has been slowing since 1980. Therefore, other factors must be considered when explaining the change in urban and rural population. Table 1: Total Population 1960 2000, Puerto Rico Total Population Percentage Change 2000 3,808,610 8% 1990 3,522,037 10% 1980 3,196,520 18% 1970 2,712,033 15% 1960 2,349,544 Source: U.S. Census Bureau In this paper I posit that an important explanation for the substantial decrease of rural population was changes to the criteria and methodology used to delineate urban and rural areas in Puerto Rico for the 1990 and 2000 censuses, although rural-to-urban migration and urban growth certainly played a role. I also discuss issues related to appropriate population density thresholds when defining urban and rural areas in Puerto Rico. 2
Criteria and Methodology from 1990 to 2000 The Census Bureau modified the criteria and methodology used to delineate urban areas for Census 2000. One of the major changes was the adoption of automated delineation software to define urban areas. For Census 2000, urban areas encompass densely settled territory consisting of core census block groups or blocks that have a population density of at least 1,000 people per square mile (ppsm) and surrounding census blocks that have an overall density of at least 500 ppsm. With the advance of technology, the Census Bureau was able to automate the urban area delineation process to ensure a more accurate and consistent representation of urban landscape for Census 2000. For the 1990 census, however, Census Bureau geographers interactively reviewed population density patterns to delineate urbanized areas. Census blocks were grouped to form analysis units based either on similar street patterns or similar density patterns. If the overall density of blocks within an analysis unit met the minimum threshold of at least 1,000 ppsm, all blocks were included in the urbanized area (Figure 1). This approach allowed for the inclusion of blocks with non-residential urban land uses such as parks, schools, or commercial development that had densities less than 1,000 ppsm. Figure 1: 1990 Urbanized Areas Criteria United States The Census Bureau applied a slightly different methodology in delineating urbanized areas in Puerto Rico for the 1990 census. When reviewing density patterns in Puerto Rico, we were concerned that if we applied the same methodology as was applied in the 3
United States we would substantially overbound the extent of urbanized areas. Therefore, we decided to include in urbanized areas only those census blocks that had densities of at least 1,000 ppsm and to exclude any block with a density less than 1,000 ppsm (Figure 2). Figure 2: 1990 Urbanized Areas Criteria Puerto Rico As a result of this methodological change, territory that might have been classified as urban under the methodology used for the United States was classified as rural in Puerto Rico in 1990. The application of what amounted to a stricter methodology resulted in a definition of urbanized areas that, at the time, was considered to be a more accurate and consistent definition. The unforeseen consequence, however, was that adoption of an automated delineation process for Census 2000, coupled with criteria changes, would lead to substantial increases in urban territory and population perhaps more substantial than would have been obtained had we applied the same method in Puerto Rico that was applied in the United States in 1990. To further illustrate how changes in criteria and methodology impact urban population in Puerto Rico, I compare 1990 data with 1990(former) criteria and 1990(current) criteria (Figure 3). Between 1990 and 2000, the percent of urban population increased substantially from 71 percent to 94 percent of total population, a 23 percentage point increase. However, when we applied the 2000 criteria to 1990 data (1990 current criteria), the urban population was about 3.3 million, or about 93 percent of the total population, yielding a percentage point increase of only 1.4 (Map 2, Map 3). We can assume from this that, had we applied the state-side method to Puerto Rico in 1990, the urban population in Puerto Rico for 1990 likely would have been close to 90 percent. While this would have reduced the percentage point change between 1990 (former 4
criteria) and 2000, it would have represented a substantial change between 1980 and 1990. The fact of the matter is that a substantial increase in population as a result of criteria and methodological changes would have occurred at some time if not 1990 to 2000, then 1980 to 1990. Figure 3: 1990 Former and Current Criteria Examples This section illustrates how the change in methodology and criteria affected the delineation of urban areas in Puerto Rico. I will examine municipios that have the greatest percentage change in urban population between 1990 and 2000, and discuss its relationship to population growth, and migration. 1. Map 4 identifies the top 10 municipios that have greatest percentage point change in urban population between 1990 and 2000. These municipios were predominately rural under the 1990 former definition, but were predominately urban under the 2000 definition. When we applied the 2000 criteria to 1990 data, most of these municipios were included in the 1990 current criteria urban areas. Rincon municipio, for example, was 100 percent rural under the 1990 (former) definition, but 100 percent urban under both the 1990 (current) definition and 2000 definition. In other words, if we were using the same criteria as in 2000 in delineating urban areas in Rincon municipio in 1990, Rincon would have been 100 percent urban and the percentage 5
change in urban population for Rincon would be zero between 1990 and 2000, rather than 100. Similar changes are seen in other municipios when we compare data with the 1990 current definition. Instead of being only 30 percent urban in 1990, these municipios would have over 80 percent of total population in urban areas under the 1990 current definition. Instead of having a substantial increase of percent urban in 2000 (between 60 and 100 percentage point increase), there was only a minimal percentage point increase when comparing data with 1990 current definition. Villalba municipio experienced a percentage point change of -1 when comparing data with 1990 current definition. Such a marked difference in urban population between the 1990 former and the current definition demonstrated that criteria and methodological changes are the major factors causing a substantial increase in urban population in Puerto Rico. As the population density for much of the territory in these municipios was below 1,000 ppsm, they were for the most part excluded from urbanized areas in 1990. For instance, as shown in Map 5, most of the blocks in Rincon municipio had a population density between 500 to 1,000 ppsm; most of the blocks with densities of 1,000 ppsm were not adjacent to other qualifying territory, and therefore were excluded from any urbanized area in 1990. Lowering the population density threshold and the changes affecting hops and jumps under the current definition qualified territory in Rincon for inclusion in urban areas. 2. We were also interested in knowing whether some of these municipios had experienced substantial in-migration between 1995 and 2000. As shown in Map 6, there is not a strong relationship between migration across municipios and urban growth among these municipios. Some of these municipios were only showing a moderate net migration gain within a range of 1 person to 2,500 numbers of people during 1995 to 2000. There was even a net migration loss for Rincon municipio, as well as for some other municipios. 3. The unique population distribution pattern of Puerto Rico also plays an important role in affecting its urban morphology. Puerto Rico is a densely populated area with over 90 percent of its residents live in areas with population density of at least 500 ppsm. As Map 7 shows, the shaded areas were excluded from urbanized areas in 1990 because they did not meet the requirement of overall density of 1,000 ppsm. The population density for most of these areas was between 500 to 1,000 ppsm. For Census 2000, nearly all the population was within urban areas with at least 500 ppsm (Map 8). When comparing data with 1990 current definition and 2000 definition, the newly added urban areas were fringe of 1990 urbanized areas based on current definition. Most of these areas have a population density between 500 and 1,000 ppsm (Map 9). 6
What s Next? The Geography Division plans to continue research pertaining to the delineation of urban areas for Puerto Rico for Census 2010. This research is focusing primarily on identifying the minimum population density threshold that will allow the most appropriate separation of urban and rural territory. Puerto Rico s population is densely settled in general, with over 90 percent of its population residing in areas with population density of at least 500 ppsm (Table 2). If we change the population threshold to 1,000 ppsm, the cumulative percent of total population would still be over 80 percent. Decisions such as whether we should keep the criteria the same in Puerto Rico as in the rest of the United States, or whether we should change the population threshold for Puerto Rico so to better represent its unique urban landscape become important issues as we revisit urban areas criteria for the Census 2010. Table 2: Estimated Total Number of People by Population Density Per Square Mile, 2000 Cumulative Pop Density ppsm Total Pop Percent of Total Pop Percent of Total Pop Cumulative Pop 0 to 499 298,914 8% 500 to 999 333,835 9% 92% 3,509,696 1,000 to 1,499 240,342 6% 83% 3,175,861 1,500 to 1,999 173,579 5% 77% 2,935,519 2,000 to 2,499 127,255 3% 73% 2,761,940 2,500 to 2,999 109,436 3% 69% 2,634,685 3,000 to 3,499 90,496 2% 66% 2,525,249 3,500 to 3,999 70,905 2% 64% 2,434,753 4,000 to 4,499 71,122 2% 62% 2,363,848 4,500 to 4,999 71,275 2% 60% 2,292,726 5,000 to 5,499 2,221,451 58% 58% 2,221,451 Source: U.S. Census Bureau Conclusion In summary, an important explanation for the urban/rural shift in Puerto Rico was a change in criteria and methodology used in delineating urban areas for the 1990 and 2000 censuses. When we applied the 2000 criteria to 1990 census data, the percent of urban population changed from 71 percent (with the 1990 former definition) to 93 percent (with the 1990 current definition). This new urban territory was not included in urbanized areas defined under the 1990 former criteria because blocks contained within generally had population densities below 1,000 ppsm and therefore did not meet the modified requirements. Because of the different methodology used between 1990 and 2000, 7
municipios that were predominately rural under the 1990 former definition had become predominately urban under both the 1990 current definition and 2000 definitions. 8
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