The estimates of this study confirm that human capital has a significant and positive effect on labor productivity in Chinese enterprises. In addition, they show that this effect varies across enterprises with different values of productivity. Moreover, they reveal the mediating role of innovation in this effect.
Table 2 represents the results of estimating the relationship between human capital indicators and productivity in Model (1). According to the results, the coefficients of education level including college, undergraduate, master, and doctorate degrees are 0.110, 0.205, 0.419, and 0.517, respectively, which are positive, increasing, and significant at 1% level, except for the college degree, significant at 10% level. Due to the ascending order of the estimated coefficients, the results show that labors with higher education levels have greater impacts on productivity. Regarding the technical skills, the coefficient of elementary rank is -0.014, negative and statistically insignificant. However, the coefficients of people with senior and middle ranks are 0.168 and 0.145, which are positive and statistically significant at 5% and 1% level, respectively. These estimates, similar to the effects of education indicators, show that labors with high skills have a stronger influence on productivity. Likewise, the experience indicators follow an increasing order. Accordingly, they are 0.277, 0.375, and 0.469 for people with 1–3 years, 1–5 years, and more than 5 years, respectively, which are positive, ascending, and statistically significant at 1% level. Therefore, all three dimensions of human capital including education, technical skills, and experience show a constructive effect on productivity level, confirming hypothesis 1 (H1).
The estimation of Model (1) involves the results of two additional tests including the VIF and Hausman test. The Hausman test rejects its null hypothesis, implying that the model follows a fixed-effects pattern. In addition, the results of VIF range within 1.07 and 2.52 rejecting any serious multicollinearity issues. Therefore, Model (1) is estimated using a fixed-effects model, whose results are valid due to no serious multicollinearity.
Table 2
Estimated impact of human capital on productivity in Model (1)
Variable | Coefficient (t-statistics) | VIF price |
Education | | |
College | 0.110* | 1.83 |
| (1.95) | |
Undergraduate | 0.205*** | 1.89 |
| (4.18) | |
Master | 0.419*** | 1.48 |
| (4.44) | |
Doctor | 0.517*** | 1.22 |
| (2.77) | |
Skill | | |
Elementary | -0.014 | 1.07 |
| (-0.32) | |
Middle | 0.145*** | 1.14 |
| (3.10) | |
Senior | 0.168** | 1.23 |
| (2.40) | |
Experience | | |
1 ~ 3 years | 0.277*** | 2.16 |
| (6.58) | |
3 ~ 5 years | 0.375*** | 1.68 |
| (8.11) | |
> 5 years | 0.469*** | 2.52 |
| (9.44) | |
Constant | 4.150*** | |
| (36.58) | |
Note: Parentheses show t-statistics. *, **, and *** represent statistical significance at 10%, 5%, and 1%, levels, respectively. |
The results of the robustness tests validate the estimates of Model (1). Table 3 represents the results of the robustness tests. The results of all three robustness tests confirm the beneficial effects of human capital on productivity. In addition, they indicate a higher effect among people with higher education, technical skills, and experience, consistent with the results of Model (1). For example, the results of the bilateral censoring method indicate that the coefficients of education indicators including college, undergraduate, master, and doctorate degrees are 0.074, 0.165, 0.354, and 0.522, respectively. They are positive and statistically significant at 1% level, except for the statistically insignificant college degree. They indicate an increasing order. In addition, the coefficients of the technical skill indexes including middle and senior ranks are 0.146, and 0.172, respectively, which are positive and statistically significant at 1% level, respectively. Although the coefficient of the elementary level is -0.020, which is negative and statistically insignificant, the three estimated coefficients display an ascending order, confirming the results of Model (1). Moreover, the coefficients of experience indicators including 1–3, 3–5, and more than 5 years are 0.280, 0.380, and 0.480, respectively, which are statistically significant at 1% level. According to these results, all the estimated coefficients of the robustness tests affirm that labor with higher education, technical skills, and experience have a stronger beneficial effect on productivity, verifying the results of estimating Model (1). Therefore, the results of Model (1) are stable, robust, and valid.
Table 3
Results of the robustness tests on the impact of human capital on productivity
Method | Variable replacement | Panel tool variable | Bilateral censoring |
Variable | Coefficient (t-statistics) | Coefficient (t-statistics) | Coefficient (t-statistics) |
Education | | | |
College | 0.257*** | 0.109** | 0.074 |
| (4.01) | (2.36) | (1.62) |
Undergraduate | 0.376*** | 0.200*** | 0.165*** |
| (6.50) | (4.90) | (4.12) |
Master | 0.591*** | 0.413*** | 0.354*** |
| (5.67) | (6.17) | (4.93) |
Doctor | 0.674*** | 0.510*** | 0.522*** |
| (3.33) | (4.86) | (3.54) |
Skill | | | |
Elementary | 0.022 | -0.013 | -0.020 |
| (0.49) | (-0.37) | (-0.55) |
Middle | 0.248*** | 0.147*** | 0.146*** |
| (4.66) | (4.07) | (4.03) |
Senior | 0.131 | 0.165*** | 0.172*** |
| (1.52) | (3.08) | (2.96) |
Experience | | | |
1 ~ 3 years | 0.407*** | 0.277*** | 0.280*** |
| (9.16) | (8.49) | (8.58) |
3 ~ 5 years | 0.551*** | 0.375*** | 0.380*** |
| (10.80) | (10.59) | (10.72) |
> 5 years | 0.745*** | 0.470*** | 0.480*** |
| (13.47) | (12.72) | (13.02) |
Constant | 5.482*** | | 4.186*** |
| (43.56) | | (38.75) |
Note: Parentheses show t-statistics. *, **, and *** represent statistical significance at 10%, 5%, and 1%, levels, respectively. |
Table 4 represents the results of the endogeneity tests which reject any endogeneity issue in the estimations. According to the results, supplementing the missing variables to the regression produces similar outcomes. For example, adding urbanization rate estimates the coefficients of education indicators including college, undergraduate, master, and doctorate degrees equal to 0.110, 0.205, 0.419, and 0.517, respectively. They are positive and statistically significant at 1% level, except for the coefficient of college degree which is statistically significant at 10% level. Likewise, the coefficients of technical skills indexes including middle and senior levels are 0.145 and 0.168, which are positive and statistically significant at 1% and 5% levels, respectively. Although the coefficient of the elementary level is -0.014, which is negative and statistically insignificant, the estimated coefficients follow an ascending order from the lowest to the highest technical skills, which is consistent with the results of Model (1). Moreover, the coefficients of experience years, i.e., 1–3, 3–5, and more than 5 years, are 0.277, 0.375, and 0.469, respectively, which are positive and statistically significant at 1% level. Accordingly, the results of the endogeneity tests consistently show an ascending order, implying that labors with higher education, technical skills, and experience have a more beneficial impact on productivity. Therefore, the results reject any endogeneity issues and accept the outcomes of Model (1).
Table 4
Results of the endogeneity tests on the impact of human capital on productivity
Method | Urbanization rate | CPI | Educational expenditure |
Variable | Coefficient (t-statistics) | Coefficient (t-statistics) | Coefficient (t-statistics) |
Education | | | |
College | 0.110* | 0.110* | 0.110* |
| (1.95) | (1.95) | (1.95) |
Undergraduate | 0.205*** | 0.205*** | 0.205*** |
| (4.18) | (4.18) | (4.18) |
Master | 0.419*** | 0.419*** | 0.419*** |
| (4.44) | (4.44) | (4.44) |
Doctor | 0.517*** | 0.517*** | 0.517*** |
| (2.77) | (2.77) | (2.77) |
Skill | | | |
Elementary | -0.014 | -0.014 | -0.014 |
| (-0.32) | (-0.32) | (-0.32) |
Middle | 0.145*** | 0.145*** | 0.145*** |
| (3.10) | (3.10) | (3.10) |
Senior | 0.168** | 0.168** | 0.168** |
| (2.40) | (2.40) | (2.40) |
Experience | | | |
1 ~ 3 years | 0.277*** | 0.277*** | 0.277*** |
| (6.58) | (6.58) | (6.58) |
3 ~ 5 years | 0.375*** | 0.375*** | 0.375*** |
| (8.11) | (8.11) | (8.11) |
> 5 years | 0.469*** | 0.469*** | 0.469*** |
| (9.44) | (9.44) | (9.44) |
Urbanization rate | 19.92*** | | |
| (7.36) | | |
CPI | | 1.828*** | |
| | (7.36) | |
Educational expenditure | | | 0.115*** (7.36) |
Constant | -12.76*** | 2.322*** | 3.869*** |
| (-5.62) | (9.55) | (35.38) |
R2 | 0.074 | 0.074 | 0.074 |
Note: Parentheses show t-statistics. *, **, and *** represent statistical significance at 10%, 5%, and 1%, levels, respectively. |
The results of heterogeneity tests show that human capital has a stronger impact on enterprises with higher levels of productivity. Table 5 represents the results of the heterogeneity tests, according to the different quantiles of productivity levels. According to the results, with changing the labor productivity from low to high conditional quantiles, human capital with high education and more than 3 years of working experience shows an obviously prominent role. In addition, the human capital of bachelor's degree or below, intermediate and senior skills and 1 ~ 3 years of work experience reveal a U-shape relationship. Moreover, primary-skilled human capital is a hindrance to labor productivity. Therefore, human capital has different patterns of effects among enterprises with various productivity levels, but it shows stronger effects in enterprises with a higher level of productivity, highlighting the positive role of human capital in enterprises with higher levels of productivity. This result affirms hypothesis 2 (H2).
Table 5
Estimated impacts of human capital on productivity under different conditional quantiles
Quantile | 0.1 | 0.25 | 0.5 | 0.75 | 0.9 |
Variable | Coefficient (t-statistics) | Coefficient (t-statistics) | Coefficient (t-statistics) | Coefficient (t-statistics) | Coefficient (t-statistics) |
Education | | | | | |
College | 0.303*** | 0.227*** | 0.222*** | 0.255*** | 0.304*** |
| (204.79) | (205.18) | (34.40) | (67.86) | (215.46) |
Undergraduate | 0.462*** | 0.453*** | 0.511*** | 0.538*** | 0.583*** |
| (313.63) | (416.23) | (96.96) | (154.83) | (492.39) |
Master | 0.853*** | 1.028*** | 1.062*** | 1.141*** | 1.169*** |
| (365.71) | (863.66) | (291.57) | (896.04) | (508.63) |
Doctor | -0.442*** | -0.100*** | 0.539*** | 0.662*** | 0.700*** |
| (-48.20) | (-26.93) | (43.35) | (85.14) | (110.14) |
Skill | | | | | |
Elementary | 0.049*** | -0.050*** | -0.068*** | -0.106*** | -0.156*** |
| (45.32) | (-29.51) | (-7.50) | (-17.93) | (-160.58) |
Middle | 0.107*** | 0.037*** | 0.037*** | 0.034*** | 0.056*** |
| (44.63) | (23.44) | (37.48) | (17.31) | (21.73) |
Senior | 0.161*** | 0.002* | -0.034*** | 0.148*** | 0.146*** |
| (127.93) | (1.69) | (-2.84) | (136.10) | (51.44) |
Experience | | | | | |
1 ~ 3 years | 0.211*** | 0.190*** | 0.206*** | 0.235*** | 0.291*** |
| (31.95) | (62.80) | (19.55) | (55.15) | (74.92) |
3 ~ 5 years | 0.152*** | 0.167*** | 0.176*** | 0.182*** | 0.214*** |
| (23.07) | (72.55) | (23.93) | (35.92) | (78.10) |
> 5 years | 0.282*** | 0.327*** | 0.351*** | 0.467*** | 0.646*** |
| (63.95) | (235.94) | (41.09) | (129.14) | (251.82) |
Note: Parentheses show t-statistics. *, **, and *** represent statistical significance at 10%, 5%, and 1%, levels, respectively. |
The results of the heterogeneity tests reveal that human capital has a stronger impact on the productivity level of enterprises with R&D investment than those without such investment. Table 6 represents the results of the heterogeneity tests on enterprises with and without R&D investment. According to the estimates, in terms of education and skills, the higher the academic qualifications, skill level, and length of service of human capital, the greater the promotion effect on the labor productivity of R&D enterprises. However, in non-R&D enterprises, 3–5 years of work experience, master's degree, and intermediate skilled employees have a greater impact on the labor productivity of the enterprise. It shows that employees with solid professional basic knowledge, advanced skills, and rich work experience have room to give full play to the scientific and technological innovation activities of R&D enterprises, but do not have full room for exertion in non-R&D enterprises.
Table 6
Estimated impact of human capital on productivity in Model (1) for two sample enterprises with and without R&D investment
Sample | With R&D investment | Without R&D investment |
Variable | Coefficient (t-statistics) | Coefficient (t-statistics) |
Education | 0.148** | 0.094 |
College | (1.97) | (0.91) |
| 0.210*** | 0.240** |
Undergraduate | (3.20) | (2.53) |
| 0.284** | 0.492*** |
Master | (2.16) | (2.75) |
| 0.867*** | 0.451 |
Doctor | (2.92) | (1.46) |
Skill | -0.040 | -0.056 |
Elementary | (-0.82) | (-0.60) |
| 0.144** | 0.191** |
Middle | (2.49) | (2.01) |
| 0.208** | 0.044 |
Senior | (2.13) | (0.35) |
Experience | 0.261*** | 0.331*** |
1 ~ 3 years | (4.87) | (3.85) |
| 0.324*** | 0.472*** |
3 ~ 5 years | (5.37) | (5.10) |
| 0.481*** | 0.410*** |
> 5 years | (7.30) | (4.37) |
Constant | 4.323*** | 3.845*** |
| (34.81) | (12.69) |
R2 | 0.092 | 0.060 |
Note: Parentheses show t-statistics. *, **, and *** represent statistical significance at 10%, 5%, and 1%, levels, respectively. |
The results of the mediating tests reveal that innovation has a positively mediating role in the effects of some human capital indicators on enterprises. Table 7 represents the results of estimating the mediating effects of innovation. According to the results, doctorate degree, master degree, and middle level of technical skills show a considerable mediating effect in both regressions with two different proxies of the number of effective patents and per capita technology income. In Model (2), the coefficients of doctorate degree are 0.104 and 1.051 in the case of the number of effective patents and per capita technology income, which are positive and statistically significant at 5% and 1% levels, respectively. Similarly, the coefficients of master degree are 0.044 and 1.757, which are positive and statistically significant at 1% level. Likewise, the coefficients of the middle level of technical skills are 0.023 and 0.254, which are positive and statistically significant at 5% and 1% levels, respectively. Therefore, the results of Model (2) confirm the effects of doctorate degree, master degree, and middle level of technical skills on both innovation indicators.
In addition, the results of Model (3) indicate the considerable effects of both the innovation proxies on the productivity level. The coefficients of the number of valid patents and per capita technology income are 0.188 and 0.087, respectively, which are statistically significant at 1% level. Thus, doctorate degree, master degree, and middle level of technical skills considerably affect innovation, which in turn impacts productivity. In conclusion, innovation has a mediating role in the impact of human capital on productivity, especially through labor with doctorate degree, master degree, and middle level of technical skills, supporting hypothesis 3 (H3).
Table 7
Estimated mediation role of innovation on the effects of human capital on productivity
| Model (2) | Model (3) |
Moderator | Patents | Tech income | Patents | Tech income |
Variable | Coefficient (t-statistics) | Coefficient (t-statistics) | Coefficient (t-statistics) | Coefficient (t-statistics) |
Education | | | | |
College | 0.013 | 0.824*** | 0.225*** | 0.142** |
| (1.14) | (7.09) | (3.57) | (2.52) |
Undergraduate | 0.009 | 1.374*** | 0.400*** | 0.264*** |
| (1.44) | (14.06) | (8.01) | (5.80) |
Master | 0.044*** | 1.757*** | 0.894*** | 0.695*** |
| (2.94) | (10.82) | (10.21) | (8.78) |
Doctor | 0.104** | 1.051*** | 0.322* | 0.237 |
| (2.28) | (3.31) | (1.86) | (1.59) |
Skill | | | | |
Elementary | 0.018 | 0.192** | -0.028 | -0.051 |
| (1.59) | (2.21) | (-0.58) | (-1.19) |
Middle | 0.023** | 0.254*** | 0.084* | 0.056 |
| (2.13) | (2.83) | (1.69) | (1.27) |
Senior | -0.011 | 0.318** | 0.014 | 0.002 |
| (-0.90) | (2.26) | (0.18) | (0.04) |
Experience | | | | |
1 ~ 3 years | 0.004 | 0.083 | 0.183*** | 0.189*** |
| (0.44) | (1.13) | (4.03) | (4.78) |
3 ~ 5 years | 0.028*** | -0.066 | 0.233*** | 0.248*** |
| (2.76) | (-0.77) | (4.70) | (5.69) |
> 5 years | 0.030*** | -0.146 | 0.345*** | 0.379*** |
| (3.17) | (-1.56) | (6.73) | (8.28) |
Moderator | | | | |
Patents | | | 0.188*** | |
| | | (4.06) | |
Tech income | | | | 0.0878*** |
| | | | (20.50) |
Constant | -0.003 | 3.095*** | 4.537*** | 4.212*** |
| (-0.25) | (14.00) | (45.57) | (45.77) |
R2 | 0.022 | 0.052 | 0.156 | 0.182 |
Note: Parentheses show t-statistics. *, **, and *** represent statistical significance at 10%, 5%, and 1%, levels, respectively. |