East Greenwich School Committee

From the 12/08/2021 Demographic Study presentation

School Year	Pupils (RADM)
2022-2023	2,543
2023-2024	2,554
2024-2025	2,591
2025-2026	2,607
2026-2027	2,634
2027-2028	2,631
2028-2029	2,645
2029-2030	2,644
2030-2031	2,653
2031-2032	2,661

The McKibben forecast uses a different methodology than previous enrollment projections (the Cohort-Component Method)¹

Expected future populations of age-gender cohorts are computed using a base-year population combined with age-specific fertility, mortality, and migration rates.

These are combined with historical enrollments by grade.

The required datasets are:

• The 2010 Census population for the attendance area
• A set of age-specific fertility rates for the district
• A set of age-specific mortality rates for the district
• A set of age-specific migration rates for the district
• Historical enrollment figures by grade

Actual enrollments for this graph were obtained from the RI Department of Education ² and the U.S. DOE Public Elementary/Secondary School Universe Survey Data ³

All previous projections used the Cohort Survival Ratio method

• Dr. McKibben described this as "the only game in town" until the mid-1990s
• Not a Forecast, but projections based on mechanical extrapolations of observed enrollment counts
• Very sensitive to noise in the birth counts
• Long-term projections are evidently not very stable

• 1853-1930 counts obtained from public birth records at East Greenwich Town Hall ⁴
• 1990-2020 counts obtained from various enrollment projections
• Interestingly, the data shows sharp drops in births, usually around wars and economic downturns
• There are no really big positive increases that are not recoveries from downturns

A negative binomial probability model fits the last 31 years of births quite well.

• The theoretical interquartile range is 102 to 119. We expect the number of births to fall in this range 50% of the time. In the data, 15 of 31 data points are in this range.
• The theoretical 95% probability interval is 87 to 137. We expect the number of births to fall in this range 19 times out of 20. In the data, 2 of 31 data points are outside this interval. We expect 1.5.
• In this model, the expected number of births is neither increasing nor decreasing. The fact that it fits the data pretty well indicates there is no strong evidence for a trend up or down in births.

This is a histogram of the birth count probabilities for a single year.