| Variable | lnCost | lnCost | lnCost | lnCost |
| (1) low | (2) high | (3) low | (4) high | |
| constant | 0.006 | −0.002 | 0.005 | −0.002 |
| (0.43) | (−0.12) | (0.37) | (−0.11) | |
| lnRev | 0.907*** | 0.917*** | 0.907*** | 0.918*** |
| (41.03) | (41.95) | (41.09) | (41.96) | |
| D | −0.01 | −0.023* | −0.009 | −0.023* |
| (−0.80) | (−1.79) | (−0.71) | (−1.77) | |
| lnRev * D | −0.181*** | −0.202*** | −0.176*** | −0.201*** |
| (−3.27) | (−4.09) | (−3.20) | (−4.09) | |
| SP * lnRev * D | 0.005 | 0.024** |
|
|
|
| (0.26) | (2.18) |
|
|
| SP*lnRev | −0.005 | −0.010** |
|
|
|
| (−0.89) | (−2.23) |
|
|
| SP*D | −0.004 | 0.003 |
|
|
|
| (−0.74) | (1.43) |
|
|
| SPSC * lnRev * D |
|
| −0.000 | 0.001** |
|
|
| (−0.12) | (2.33) | |
| SPSC * D |
|
| −0.000* | −0.000** |
|
|
| (−1.94) | (−2.51) | |
| Control variables | control | control | control | control |
| Year | control | control | control | control |
| Obs | 1715 | 1913 | 1715 | 1913 |
| R-squared | 0.895 | 0.9 | 0.895 | 0.901 |