Table 1.
Price Changes in the Cohort of Generic Drugs for Calendar Periods 2008–2016
| Calendar time | 2008* | 2010* | 2012* | 2014* | 2016* |
|---|---|---|---|---|---|
| Price ratio group, n (%)† | |||||
| Overall (N = 1099) | |||||
| Increased in price | 307 (27.9) | 251 (22.8) | 315 (28.6) | 491 (44.6) | 388 (35.3) |
| 1 ≤ ref < 1.10 | 242 (22.0) | 103 (9.4) | 67 (6.1) | 46 (4.2) | 33 (3.0) |
| 1.10 ≤ ref < 2 | 62 (5.6) | 116 (10.5) | 163(14.8) | 264(24.0) | 166 (15.1) |
| 2 ≤ ref < 3 | 2 (0.2) | 19 (1.7) | 42 (3.8) | 80 (7.3) | 77 (7.0) |
| ≥ 3 ref | 1 (0.1) | 13 (1.2) | 43 (3.9) | 101 (9.2) | 112 (10.1) |
| Decreased in price | 792 (72.0) | 848 (77.1) | 784 (71.3) | 608 (55.3) | 711 (64.6) |
| 0.90 < ref < 1 | 707 (64.3) | 211 (19.1) | 102 (9.3) | 83 (7.5) | 43 (3.9) |
| 0.50 < ref ≤ 0.90 | 84 (7.6) | 606 (55.1) | 571 (51.9) | 393 (35.7) | 273 (24.8) |
| 0.33 < ref ≤ 0.5 | 1 (0.1) | 30 (2.7) | 82 (7.5) | 93 (8.5) | 196 (17.8) |
| ≤ 0.33 ref | 0 (0.0) | 1 (0.1) | 29 (2.6) | 39 (3.5) | 199 (18.1) |
| Lowest prescription frequency group (n = 366)‡ | |||||
| Increased in price | 155 (42.3) | 145 (39.6) | 163 (44.5) | 207 (56.5) | 167 (45.6) |
| 1 ≤ ref < 1.10 | 116 (31.6) | 66 (18.0) | 32 (8.7) | 15 (4.1) | 10 (2.7) |
| 1.10 ≤ ref < 2 | 38 (10.3) | 61 (16.6) | 90 (24.5) | 108 (29.5) | 67(18.3) |
| 2 ≤ ref < 3 | 1 (0.3) | 12 (3.3) | 20 (5.5) | 37 (10.1) | 34 (9.3) |
| ≥ 3 ref | 0 (0.0) | 6 (1.6) | 21 (5.7) | 47 (12.8) | 56 (15.3) |
| Decreased in price | 211 (57.6) | 221 (60.3) | 203 (55.4) | 159 (43.4) | 199 (54.3) |
| 0.90 < ref < 1 | 175 (47.8) | 78 (21.3) | 44 (12.0) | 28 (7.7) | 18 (4.9) |
| 0.50 < ref ≤ 0.90 | 35 (9.6) | 136 (37.1) | 136 (37.1) | 102 (27.8) | 106 (28.9) |
| 0.33 < ref ≤ 0.5 | 1 (0.3) | 7 (1.9) | 18 (4.9) | 19 (5.2) | 36 (9.8) |
| ≤ 0.33 ref | 0 (0.0) | 0 (0.0) | 5 (1.4) | 10 (2.7) | 39 (10.6) |
| Middle prescription frequency group (n = 367)‡ | |||||
| Increased in price | 105 (28.6) | 74 (20.2) | 101 (27.5) | 180 (49.1) | 148 (40.4) |
| 1 ≤ ref < 1.10 | 84 (22.9) | 29 (7.9) | 21 (5.7) | 20 (5.5) | 9 (2.5) |
| 1.10 ≤ ref < 2 | 20 (5.5) | 36 (9.8) | 51 (13.9) | 92 (25.1) | 68 (18.5) |
| 2 ≤ ref < 3 | 1 (0.3) | 5 (1.4) | 14 (3.8) | 31 (8.5) | 35 (9.6) |
| ≥ 3 ref | 0 (0.0) | 4 (1.1) | 15 (4.1) | 37 (10.1) | 36 (9.8) |
| Decreased in price | 262 (71.5) | 293 (80.0) | 266 (72.6) | 187 (51.0) | 219 (59.8) |
| 0.90 < ref < 1 | 244 (66.6) | 77 (21.0) | 36 (9.8) | 30 (8.2) | 11 (3.0) |
| 0.50 < ref ≤ 0.90 | 18 (4.9) | 211 (57.6) | 209 (57.1) | 134 (36.6) | 96 (26.2) |
| 0.33 < ref ≤ 0.5 | 0 (0.0) | 4 (1.1) | 16 (4.4) | 16 (4.37) | 70 (19.1) |
| ≤ 0.33 ref | 0 (0.0) | 1 (0.3) | 5 (1.4) | 7 (1.91) | 42 (11.4) |
| Highest prescription frequency group (n = 366)‡ | |||||
| Increased in price | 47 (12.8) | 32 (8.74) | 51 (13.9) | 104 (28.4) | 73 (19.9) |
| 1 ≤ ref < 1.10 | 42 (11.4) | 8 (2.2) | 14 (3.8) | 11 (3.0) | 14 (3.8) |
| 1.10 ≤ ref < 2 | 4 (1.09) | 19 (5.2) | 22 (6.0) | 64 (17.4) | 31 (8.5) |
| 2 ≤ ref < 3 | 0 (0.0) | 2 (0.5) | 8 (2.2) | 12 (3.23) | 8 (2.2) |
| ≥ 3 ref | 1 (0.3) | 3 (0.8) | 7 (1.9) | 17 (4.6) | 20 (5.5) |
| Decreased in price | 319 (87.1) | 334 (91.2) | 315 (86.0) | 262 (71.5) | 293 (80.0) |
| 0.90 < ref < 1 | 288 (78.6) | 56 (15.3) | 22 (6.0) | 25 (6.8) | 14 (3.8) |
| 0.50 < ref ≤ 0.90 | 31 (8.4) | 259 (70.7) | 226 (61.7) | 157 (42.8) | 71 (19.3) |
| 0.33 < ref ≤ 0.5 | 0 (0.0) | 19 (5.2) | 48 (13.1) | 58 (15.8) | 90 (24.5) |
| ≤ 0.33 ref | 0 (0.0) | 0 (0.0) | 19 (5.2) | 22 (6.0) | 118 (32.2) |
Drug-specific price ratios were estimated using prices from the first half of 2008 as reference; the cohort was comprised of 1099 generic drugs
*Data for second half of the calendar year are presented
†Categories of price change ratios were calculated by dividing the price of a drug in each period by their reference (baseline) value estimated in the first half of 2008
‡Baseline prescribing frequency was estimated by dividing the number of study-drug dispensings by the total number of dispensings in the baseline period; using terciles, study drugs were grouped into three prescription frequency groups, with the highest tercile corresponding to the most commonly prescribed drugs