Please answer three questions by reading follow article. Thank you.

Ting Chen, James Kung, and Chicheng Ma. 2020. "Long Live Keju! The Persistent Effects of China's Imperial Examination System." The Economic Journal 1-35 DOI: 10.1093/ej/ueaa043.

Article PDF Link:

https://academic.oup.com/ej/article/130/631/2030/5819954?login=true

1. Why did the authors use average river distance to pine and bamboo habitats instead of major printing centers as identification.

2. How did they rule out the concern that their IV: (a) is unlikely to be correlated with economic prosperity both past and present, and (b) will not affect human capital outcomes today via the printing channel?

3. Explain briefly the strategy adopted by the authors in accounting for the channel of cultural transmission. What is the rationale for using rare surnames to check robustness? Are the results compromised?