TABLE 3.
Forecast Accuracy of Model When Predicting Budget in Year After Formulary Change
| Y1FC Predicted, $ | Y1FC Empirical, $ | Difference (Empirical–Predicted), $ | Percentage Error | Absolute Scaled Error | |
|---|---|---|---|---|---|
| A. Forecast Accuracy of Y1FC Budget | |||||
| AntiDM_dir | |||||
| Utilization | 815,391,798 | 716,121,489 | -99,270,309 | -14 | 2.51 |
| -Rebate | -102,226,967 | -86,815,930 | 15,411,037 | -18 | 2.93 |
| -Copay | -28,198,789 | -22,559,024 | 5,639,765 | -25 | 1.25 |
| +Dispensing fee | 2,496,055 | 1,948,811 | -547,243 | -28 | 1.12 |
| =Net budget | 687,462,097 | 608,695,347 | -78,766,750 | -13 | 2.60 |
| Side effect | |||||
| Utilization | 19,562,776 | 12,729,267 | -6,833,509 | -54 | 1.81 |
| -Rebate | -3,970,627 | -2,440,100 | 1,530,528 | -63 | 1.83 |
| -Copay | -3,987,568 | -3,551,600 | 435,968 | -12 | 0.91 |
| +Dispensing fee | 713,334 | 619,841 | -93,494 | -15 | 2.31 |
| =Net budget | 12,317,916 | 7,357,408 | -4,960,507 | -67 | 1.44 |
| Mean | -31 | 1.87 | |||
| Median | -21 | 1.82 | |||
| B. Forecast Accuracy of Y1FC Budget When Assuming No Trend | |||||
| AntiDM_dir | |||||
| Utilization | 742,100,535 | 716,121,489 | -25,979,045 | -4 | 0.66 |
| -Rebate | -93,619,827 | -86,815,930 | 6,803,897 | -8 | 1.30 |
| -Copay | -27,767,038 | -22,559,024 | 5,208,014 | -23 | 1.15 |
| +Dispensing fee | 2,443,241 | 1,948,811 | -494,429 | -25 | 1.01 |
| =Net budget | 623,156,911 | 608,695,347 | -14,461,564 | -2 | 0.48 |
| Side effect | |||||
| Utilization | 16,495,704 | 12,729,267 | -3,766,437 | -30 | 1.00 |
| -Rebate | -3,276,836 | -2,440,100 | 836,736 | -34 | 1.00 |
| -Copay | -3,826,162 | -3,551,600 | 274,562 | -8 | 0.57 |
| +Dispensing Fee | 659,956 | 619,841 | -40,116 | -6 | 0.99 |
| =Net budget | 10,052,662 | 7,357,408 | -2,695,254 | -37 | 0.78 |
| Mean | -18 | 0.89 | |||
| Median | -15 | 0.99 | |||
AntiDM_dir = antidiabetic drugs directly affected by formulary changes; Y1FC = Year 1 formulary change.