Table 2.
Linear Fixed Effects Models of Generic and Brand Prescription Drug Utilization† (N=1,074)
| Variable | Number of Generic rxs PMPQ | Number of Brand rxs PMPQ | Generic Dispensing Rate (GDR) |
|---|---|---|---|
| Two-tier member cost sharing‡ | |||
| Retail coinsurance | −0.14676*** | −0.06591 | −0.00369* |
| (0.05355) | (0.07022) | (0.00218) | |
| Retail generic OOP cost | 0.04089 | 0.08753*** | 0.00203 |
| (0.02779) | (0.02841) | (0.00144) | |
| Retail generic OOP cost squared | −0.00191 | −0.00369** | −0.00019** |
| (0.00158) | (0.00167) | (0.00007) | |
| Retail brand OOP cost | −0.00068 | −0.02626*** | 0.00185*** |
| (0.00318) | (0.00371) | (0.00048) | |
| Retail brand OOP cost squared | 0.00005 | 0.00023*** | −0.00001 |
| (0.00004) | (0.00005) | (0.00001) | |
| Mail–retail generic OOP cost ratio | 0.07409 | 0.08903 | 0.00784** |
| (0.06215) | (0.05609) | (0.00366) | |
| Mail–retail generic OOP cost ratio squared | −0.00607 | −0.01230** | −0.00071** |
| (0.00572) | (0.00585) | (0.00032) | |
| Mail–retail brand OOP cost ratio | −0.20046*** | −0.29762*** | 0.02063*** |
| (0.04560) | (0.05356) | (0.00421) | |
| Mail–retail brand OOP cost ratio squared | 0.01040*** | 0.01442*** | −0.00093*** |
| (0.00245) | (0.00270) | (0.00019) | |
| Three-tier member cost sharing§ | |||
| Retail coinsurance | −0.03202 | −0.01371 | 0.00237 |
| (0.04646) | (0.04242) | (0.00178) | |
| Retail generic OOP cost | −0.02924*** | −0.00117 | 0.00016 |
| (0.00893) | (0.00796) | (0.00024) | |
| Retail generic OOP cost squared | 0.00046*** | −0.00000 | 0.00001* |
| (0.00015) | (0.00013) | (0.00001) | |
| Retail P brand OOP cost | 0.01825 | 0.00812 | −0.00136** |
| (0.01418) | (0.01736) | (0.00066) | |
| Retail P brand OOP cost squared | −0.00046** | −0.00036 | 0.00004*** |
| (0.00023) | (0.00029) | (0.00001) | |
| Retail NP brand OOP cost | 0.00539 | −0.01147* | 0.00220*** |
| (0.00514) | (0.00605) | (0.00033) | |
| Retail NP brand OOP cost squared | −0.00005 | 0.00009* | −0.00002*** |
| (0.00004) | (0.00005) | (0.00000) | |
| Mail–retail generic OOP cost ratio | 0.00711 | 0.03365* | −0.00224 |
| (0.01784) | (0.01884) | (0.00152) | |
| Mail–retail generic OOP cost ratio squared | −0.00155** | −0.00281*** | 0.00024*** |
| (0.00066) | (0.00103) | (0.00008) | |
| Mail–retail P brand OOP cost ratio | −0.18369 | −0.33670 | 0.01737*** |
| (0.24897) | (0.25856) | (0.00569) | |
| Mail–retail P brand OOP cost ratio squared | 0.05462 | 0.06557 | −0.00374** |
| (0.06402) | (0.06305) | (0.00149) | |
| Mail–retail NP brand OOP cost ratio | −0.18311 | 0.09793 | −0.01081** |
| (0.14503) | (0.19889) | (0.00461) | |
| Mail–retail NP brand OOP cost ratio squared | 0.02352 | −0.03603 | 0.00371*** |
| (0.02630) | (0.03585) | (0.00090) | |
| Other pharmacy benefit design elements | |||
| Retail deductible | −0.14751*** | −0.12812*** | −0.00042 |
| (0.03862) | (0.02930) | (0.00241) | |
| Retail dispense as written penalty (physician) | 0.00169 | −0.04776 | 0.01146*** |
| (0.02049) | (0.03002) | (0.00191) | |
| Retail dispense as written penalty (patient) | 0.05308 | 0.07999 | 0.00319** |
| (0.04452) | (0.05108) | (0.00163) | |
| Retail maximum allowable benefit | 0.06779*** | 0.05775*** | 0.01356*** |
| (0.00847) | (0.01371) | (0.00125) | |
| Retail maximum out-of-pocket | −0.02789 | −0.10436 | −0.00291 |
| (0.12390) | (0.11194) | (0.00343) | |
| Mandatory mail | 0.00480 | 0.01394 | −0.00320*** |
| (0.00921) | (0.00934) | (0.00067) | |
Note: Presented are coefficient estimates with robust Driscoll–Kraay standard errors in parentheses.
Included in models but not reported are 11 plan sponsor characteristic variables, 11 time dummies, and a constant.
Statistic1al significance denoted as:
p<.01.
p<.05.
p<.10.
Prescription drug utilization measures calculated using 30-day supply equivalents (i.e., 1 mail rx=3 retail rxs).
Coefficients and standard errors are of member cost-sharing variables interacted with two-tier plan indicator.
Coefficients and standard errors are of member cost-sharing variables interacted with three-tier plan indicator.
NP brand, nonpreferred brand; OOP, out-of-pocket; P brand, preferred brand; PMPQ, per member per quarter.