Green returns to education: Does education affect pro-environmental attitudes and behaviors in China?

continuous variable that falls between zero and one. Specifically, CSL equals one if the individ- ual is fully affected by the compulsory schooling law (i.e. aged 6 or below) and equals zero if he/she is completely unaffected by the law (i.e. aged 16 or above). For those whose ages were between 6 and 16 when the law was enforced, we define CSL as (16 –year of implementation + year of birth)/9, a decreasing linear function of age. Fig 4 illustrates the construction of the instrumental variable. Note that in constructing the instrumental variable, we take into account the fact that the year of implementation varies across provinces as shown in S1 Table in S1 Appendix. In other words, for individuals of the same age, their exposures to the CSL may differ due to the differences in the timing of the CSL in the provinces they lived. Using the instrument CSL, we re-estimate the effect of education on pro-environmental attitudes and behaviors by the two-stage least squares (2SLS) approach: Educationij ¼ a0 þ a1CSLij þ a2Xij þ a3Ch þ a4Cityk þ Zij; ð2Þ Yij ¼ b0 þ b1 d Educationij þ b2Xij þ b3Ch þ b4Cityk þ eij; ð3Þ where Eqs (2) and (3) are the first stage and second stage regressions, respectively. d Educationij represents the fitted value of Educationij from the first stage regression, and the other variables are the same as in Eq (1). Again, we cluster standard errors at the cohort-city level. Fig 4. Construction of instrumental variable. Note: This figure illustrates the construction of instrumental variable.

The X-axis is the individual age at the implementation of the CSL and the Y-axis is the individual exposure to CSL, which equals to one if the individual is fully affected by CSL (i.e. aged 6 or below) and equals to zero if the individual is unaffected by CSL (i.e. age 16 or above). A linear function is assumed for the ages in between. https://doi.org/10.1371/journal.pone.0263383.g004 PLOS ONE Green returns to education PLOS ONE | https://doi.org/10.1371/journal.pone.0263383 February 3, 2022 10 / 20