Tuesday, June 13, 2006

Demographic Predictions, Not Facts

The Superintendent's plan closes too many schools, relying on demographic predictions as if they were facts. School Board members should remember that:

#1) Demographic forecasts are uncertain.
The inherent uncertainty in demographic forecasts means that best practice requires looking at several demographic projections, using different methods or different assumptions, to see the consequences of uncertainty on the data. A school enrollment consultant for California schools provides “a range of enrollment forecasts (such as Low, Medium, and High forecasts) to indicate the level of uncertainty in the forecast and the range within which future enrollments are likely to fall.”

The Seattle School District demographic forecasts, by contrast, present one number, not a range of numbers, and do not explain what level of uncertainty is inherent in the forecast.

#2) The smaller the population, the larger the chance of error in demographic forecasting. Because of this, important policy decisions with long-term consequences should not be based on neighborhood-level forecasts. Recent district forecasting proves this point. (See "Shifting demographics drive school-closure list.")

The School Board should not accept a school closure plan that relies so heavily on demographic predictions, both for determining the number of schools closed in each cluster, and even for deciding which school in the cluster to close, when the district’s own demographer states that long-range projections for small areas can not be predicted with any accuracy.

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