| Variable | (1) Do not control the supplier | (2) lnCost |
| Constant | 0.019*** | 0.023*** |
| (3.55) | (3.86) | |
| lnRev | 0.941*** | 0.911*** |
| (66.38) | (54.5) | |
| D | −0.033*** | −0.033*** |
| (−3.70) | (−3.36) | |
| LnRev * D | −0.195** | −0.161** |
| (−2.54) | (−2.08) | |
| SS |
| −0.023 |
|
| (−1.18) | |
| SS * LnRev * D |
| −0.231* |
|
| (−1.79) | |
| SS * LnRev |
| −0.01 |
|
| (−0.27) | |
| SS * D |
| 0.165*** |
|
| (3.07) | |
| AI | −0.002 | −0.002 |
| (−1.16) | (−1.04) | |
| AI * LnRev * D | 0.007 | 0.009 |
| (0.85) | (1.08) | |
| AI * LnRev | −0.023*** | −0.024*** |
| (−4.16) | (−4.33) | |
| AI * D | 0.010*** | 0.010*** |
| (3.32) | (3.35) |