Table 4. Results of heterogeneity test.
| Variable | (1) | (2) | (3) | (4) |
|---|---|---|---|---|
| Eastern and central cities | Western and northeastern cities | First- and second-tier cities | Third-tier and below cities | |
| Digit | 0.860* | 4.675** | 1.417** | 5.312*** |
| (1.953) | (2.387) | (2.462) | (3.419) | |
| fdi | 0.042*** | 0.024** | 0.041*** | 0.032** |
| (2.770) | (2.278) | (7.681) | (2.153) | |
| is | -0.024*** | -0.018 | -0.024*** | -0.020** |
| (-3.256) | (-1.537) | (-4.782) | (-2.258) | |
| grp | 0.496*** | 1.920*** | 0.040 | 1.644*** |
| (3.839) | (3.209) | (0.708) | (3.704) | |
| lnhr | 0.010 | 1.527*** | 0.036 | 0.918*** |
| (0.128) | (2.742) | (0.478) | (3.137) | |
| lnrd | -0.147*** | 0.348 | -0.261*** | 0.380*** |
| (-2.699) | (1.546) | (-2.248) | (3.337) | |
| Constant | 13.610*** | 8.898*** | 15.571*** | 10.353*** |
| (32.165) | (10.455) | (47.308) | (14.819) | |
| City effect | Yes | Yes | Yes | Yes |
| Year effect | Yes | Yes | Yes | Yes |
| Observations | 2505 | 1770 | 735 | 3540 |
Notes: The t-statistic in parenthesis.
***, **, and * indicate statistically significant at 1%, 5%, and 10%, respectively.