Uncertainty in Forecasting
Uncertainty in Forecasting
Uncertainty in Forecasting
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ARIMA Models: States<br />
68 % Prediction Intervals, Forecasts of Selected States<br />
Average of Half-Widths 1<br />
Base Period Length (<strong>in</strong> Years)<br />
Model 10 30 50<br />
ARIMA (1,1,0)<br />
Forecast<br />
Horizon<br />
(<strong>in</strong> Years)<br />
10 9.1 7.3 6.0<br />
20 14.3 10.8 8.9<br />
30 18.5 13.5 10.9<br />
ARIMA (2,2,0)<br />
ARIMA ln(0,1,1)<br />
Forecast<br />
Horizon<br />
(<strong>in</strong> Years)<br />
Forecast<br />
Horizon<br />
(<strong>in</strong> Years)<br />
10 30 50<br />
10 35.5 22.2 16.4<br />
20 93.8 54.2 39.4<br />
30 169.8 90.1 64.9<br />
10 30 50<br />
10 9.7 8.5 7.5<br />
20 17.2 13.6 11.7<br />
30 25.3 18.5 15.4<br />
Percent of Observed Population Counts With<strong>in</strong> Interval<br />
Base Period Length (<strong>in</strong> Years)<br />
Model 10 30 50<br />
ARIMA (1,1,0)<br />
ARIMA (2,2,0)<br />
ARIMA ln(0,1,1)<br />
Forecast<br />
Horizon<br />
(<strong>in</strong> Years)<br />
Forecast<br />
Horizon<br />
(<strong>in</strong> Years)<br />
Forecast<br />
Horizon<br />
(<strong>in</strong> Years)<br />
10 50% 50% 33%<br />
20 42% 42% 17%<br />
30 42% 42% 42%<br />
10 30 50<br />
10 83% 92% 83%<br />
20 100% 92% 92%<br />
30 100% 100% 100%<br />
10 30 50<br />
10 50% 58% 58%<br />
20 67% 67% 58%<br />
30 58% 67% 67%<br />
J. Tayman, S. Smith, & J. L<strong>in</strong>. 2007.<br />
Precision, Bias, and <strong>Uncerta<strong>in</strong>ty</strong> for<br />
State Population Forecasts: An<br />
Exploratory Analysis of Time Series<br />
Models. Population Research and<br />
Policy Review 26: 347-369<br />
1 Half-Width = ((Upper Limit - Lower Limit) / 2 ) / Po<strong>in</strong>t Forecast<br />
COG/MPO Model<strong>in</strong>g Conference, July 17, 2009, San Diego, CA<br />
23
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