AK 2024 General — xgboost

Likely-voter model for AK 2024 GENR, training target election held Nov 5, 2024.

Test ROC AUC

0.8890

Brier

0.1328

Log loss

0.4137

Positive rate (training)

58%

Eligible voters: 588233

Training sample: 470586

Test sample: 117647

Methodology

Likely-voter model for 2024 GENR, fitted as an XGBoost gradient-boosted classifier on voter-history and demographic features from the AK Division of Elections statewide voter file. Trained on n=470,586 eligible voters (target positive rate 57.6%); test ROC AUC 0.8890; Brier 0.1328. Most-important features (gain): voted_2022_general (0.745), years_since_last_vote (0.073), voted_2022_primary (0.036), voted_2020_general (0.033), ever_voted_general (0.017), n_prior_generals (0.015), n_prior_elections (0.012), years_registered (0.010).

Feature importance (XGBoost gain)

Rank	Feature	gain
1	voted_2022_general	0.7449
2	years_since_last_vote	0.0727
3	voted_2022_primary	0.0364
4	voted_2020_general	0.0334
5	ever_voted_general	0.0166
6	n_prior_generals	0.0147
7	n_prior_elections	0.0118
8	years_registered	0.0096
9	party_U	0.0091
10	party_R	0.0062
11	years_at_district	0.0053
12	voted_2016_general	0.0048
13	party_D	0.0031
14	gender_F	0.0030
15	ever_voted_municipal	0.0029
16	ever_voted_primary	0.0028
17	pra_flag_int	0.0025
18	share_mail	0.0024
19	n_prior_special	0.0017
20	age_at_election	0.0016
21	n_prior_municipal	0.0016
22	share_polls	0.0014
23	n_prior_primaries	0.0013
24	voted_2020_primary	0.0011
25	party_OTHER	0.0011
26	share_absentee	0.0010
27	share_early	0.0010
28	share_questioned	0.0010
29	party_N	0.0009
30	gender_M	0.0008
31	voted_2018_general	0.0008
32	voted_2018_primary	0.0007
33	gender_U	0.0006
34	party_G	0.0006
35	party_L	0.0004

Calibration — predicted vs. actual turnout by decile

Decile (10 = highest LV)	n	Pred. p	Actual turnout
10	58824	0.991	0.994
9	58823	0.952	0.959
8	58823	0.901	0.904
7	58824	0.830	0.829
6	58823	0.710	0.710
5	58823	0.530	0.534
4	58824	0.385	0.384
3	58823	0.248	0.243
2	58823	0.138	0.132
1	58823	0.075	0.071

Eligible scored voters bucketed into 10 equal-size deciles by predicted probability. A well-calibrated model has predicted p ≈ actual turnout in every decile.

Hyperparameters

{'seed': 42, 'max_depth': 5, 'subsample': 0.9, 'test_size': 0.2, 'n_estimators': 400, 'learning_rate': 0.05, 'colsample_bytree': 0.8, 'early_stopping_rounds': 30}

Trained on AK Division of Elections statewide voter file snapshot AK DoE 2025-05 at 2026-05-23 04:38 UTC.