|
|
|
School District Demographic Estimates and Projections Every school district is faced with the challenge of determining the right magnitude and best distribution of resources to meet the needs of a changing number of students each year. While the student characteristics may be similar from one year to the next, it is very important to be able to know how student demographics will change over the next several years. School system leaders and stakeholders are concerned about having the right school facilities in the right locations to best meet the needs of students. To adequately address these planning needs, student demographic estimates and projections need to be updated annually -- or evenly more frequently. Fast growing areas may need a semi-annual update to assess new information about housing developments or key business establishment changes in the area. Estimation and projection methodologies vary widely from district to district. In many districts, school district staff responsible for developing estimates and projections are not specialists and have many other responsibilities. Estimates versus Projections. The term 'estimate' as used here applies to data developed for the current or previous time period. A 'projection' refers to data developed for future time periods. In the case of decennial census data, the term estimate is also used when referring to sample-based estimates of characteristics in Census 2000 Summary File 3 or the School District Special Tabulation (and related files). In contrast, data from Census 2000 'complete-count' files (such as Summary File 1), are not estimates and are purported to be universe data values (not subject to errors of estimation). Role of Proximity. Proximity works with school systems to develop demographic estimates and projections. Proximity can help districts implement estimation and projection methodology that provide improved decisionmaking information. The estimation and projection process may be integrated with related school system processes so that they can then be updated annually with minimal outside assistance. What-If Questions. More than simply having one set of estimates and projections, school district staff are often asked "what-if" type questions. These questions typically arise in anticipation of adding a new school, changing curriculum program or similar infrastructure planning issue. To answer these questions most effectively requires that student estimates and projections be maintained at a "fine granularity" within the district -- such as census block. In this way, staff can more easily re-organize existing estimates and projections rather than attempting to re-estimate the populations and develop potentially inconsistent data. Model-Based Estimation and Projection Methodology. A methodology for developing single year of age demographic estimates and projections for a school district and school district attendance areas is summarized below. The "model-based" methodology makes use of a set of defined behavioral relationships that knit with other socioeconomic cause and effect factors. For assistance in developing estimates and projections using these methods, contact Proximity. While some of the steps, operations, and procedures are outlined below, the most important first step is establishing the overall framework and model that best fits a particular district. Census 2000 Starting Point Data. One early step in the process is to acquire Census 2000 single year of age data for each census block in the school district for the population ages under one year through age 19 as of Census 2000. The Census 2000 data will be the "starting point" for development of estimates and projections. These data are available from the Census 2000 Summary File 1 and may be downloaded using the Census Bureau FactFinder. How to Determine Which Census Blocks? If the district is coterminous with a city/place or county, the FactFinder "geo with geo" option can be used. In other cases, the school district to census block equivalence file is required. Such as file can be developed using the "geographic identifier segment" of the Census 2000 Summary File 1. One way to access the segment 1 file is to download the file via the Census FTP Server. Alternatively, Proximity has the school district to census block equivalency files implicitly contained in the C2KBLK dataset (extended DP1 file). Note in the geographic header section of the block level record that the block code and school district code are contained in the record. School System Planning and Analysis program participants can view more detailed steps using the information at http://proximityone.com/sdpa/models/c2kdata.htm. Census Blocks and School District Boundaries. The procedure described here is for a school district whose boundaries have not changed since 2000. If the boundary has changed, the procedure must be modified. For Census 2000, census blocks were geographically defined in a manner that makes a set of census block coterminous with the school district boundary. This is true for all school districts in the U.S. Limitations on Estimation/Projection Time Period. Since this method is applied to very small geographic areas, it is suggested that the annual estimation/projection time period be limited to the period 2000 to 2010. Of course, the addition or significant change in employment of one establishment in any year could significantly alter assumptions implicit in this methodology. Modified Age-Cohort Survival Method. This estimation/projection method uses a modified age-cohort survival method. In summary, the estimated population of age i in period t is equal to the surviving population of age i-1 in period t-1 plus the net migration of population of age i in period t-1 to t for the geographic area. Determining Migration. Migration is determined at the census block level by using annual change data based on the U.S. Postal Service delivery statistics data. Delivery statistics data are used to develop estimates of occupied housing units. A relationship between persons per housing unit and the estimated number of housing units is used to develop an annual estimate of population change by census block. Role of Assumptions. There are several assumptions implicit in elements of the methodology described above. In addition, it is important to make use of assumptions about population growth or decline based on other factors that the historical data cannot determine.
Controlling to Official Estimates. Though not required, total district population estimates and projections should be controlled so that they are consistent with Federal official estimates. There are no Federal school district population estimates useful for this except in cases where the district is coterminous with a city or county. Controlling district estimates to secondary sources provides a good cross-check. District estimates and projections developed using methods described here might be superior to Federal sourced estimates, so some judgment must be applied as to the usability. Determining Enrollment from Total Population Estimates/Projections. After developing estimates and projections of total population by age by census block, these data are then further disaggregated into these categories: Total Enrolled Enrolled - Public Enrolled - Private Not Enrolled Estimates and projections of the population bt type of enrollment are developed used enrollment participation rates. Baseline enrollment participation rates are developed using Census 2000 data. Validation, Calibration, Model Revisions. Estimates and projections are validated by performing a simulation of the methods to produce the known values. As an example, the process should be applied to produce current estimates of the 2003-2004 school year enrollment using the methodology. The estimates should be similar in magnitude to the reported data. Using the Estimates and Projections. More immediate uses of the estimates and projection might include three primary analyses.
|
|
|