"The plus side (of entering the industry) is that, first, you get paid more handsomely and, second, you spare yourself the grueling years you have to endure as you progress toward tenure-a permanent job contract with a university-and professorship.

"The competition for a teaching position with a top-rated university is white hot. Many who are eyeing such a position would have to wait out the many years in between doing postdoctoral research with various groups, hoping to build up connections in a relatively small circle. The uncertainty could be gnawing. And even if you are successful, there's no let-up in the pressure before you gain tenure."

Economic incentives have always played a role. Before the 2008 financial crisis, many electronic engineering-students took math lessons and switched to financial engineering, before knocking on the door of one of those financial companies on the US East Coast.

Others change majors or take additional causes simply because the number of jobs on the market is limited for what they have started with. This was especially true for Chinese biology students who came to the US a decade ago to pursue their study, with the hope of landing a job upon graduating.

This phenomenon was partly caused by an imbalance of information that seemed to exist between China and the US back then: while biology topped the wish-list for China's brightest high-school graduates, here in the US, the front-line of biological research with some of the world's best-known bio-companies, supply far outpaced demand.

Li the Purdue graduate acknowledges that it is a lot easier for a student to change majors in the US than in China, even at very advanced stages of learning.

"At the administrative level the mechanism is there to help those who change their mind. Moreover, the way some subjects are approached and taught in the US helps to bridge worlds that are traditionally apart, such as art and science studies.

"The study of mathematical modeling in political science allowed me to go into industrial engineering for a second master's degree."

Zhang Hao, a PhD student in political science at the Massachusetts Institute of Technology, agrees. "Here in the US, political science study has been greatly influenced by the introduction into the area of various scientific methods. There's a strong tendency to conduct quantitative analysis in research, which requires training in data science."

However, Zhang says he has no intention of pursuing a career other than an academic one.

"This has a lot to do with departmental cultures. MIT ranks among the top 10 in political science study in the US, and here the professors expect you to one day become their colleague."

Sun says that compared with an industry job or the position of a staff scientist, which he held at the Argonne National Laboratory, the professorship in a university provides the opportunity for wielding more power.

"Research done for industry inevitably has to take into account the commercial interests of the company. Consequently, most are geared toward application, ie, applied research. On the other hand, scientists at a national laboratory or university would usually dedicate a big chunk of their time and resources to basic research aimed at pushing the boundaries of science.