So, how has China managed to complete this feat of engineering so quickly and cheaply? One probable factor is the project's reliance on engineers who are at the start of their careers, which presumably means they command lower salaries. The average salary in China is already comparatively low from a global perspective, at around $921 (£693) a month.

What's more, the Guizhou Road & Bridge Group Co. Ltd. is wholly state-owned. This could help it sidestep the regulatory and logistical problems private companies can often experience when taking on projects of such immense scale.

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