Thursday, May 19, 2011

Much applied work in economics concerns the problem of which came first: chicken or egg. In a recent paper, Michael Hilmer and Christina Hilmer consider this problem as it applies to the context of PhD students. They investigate the early success of PhD graduates in publishing their work, and ask whether this is due to the eminence of their supervisor - or rather is it the case that supervisors with good reputations tend to attract intrinsically more able students?

In this example, the direction of causality can be inferred by examining the relative performance of students studying with different supervisors in the same doctoral programme, and by examining the relative performance of students who share the same supervisor where the supervisor works in more than one programme (usually in different institutions).

The results suggest that success is due more to the individuals' innate abilities than to the supervisors. Good supervisors tend to attract good students, but the early career publishing performance of a given supervisor's students is higher in doctoral programmes with a higher quality (that is, in programmes which likely attract more able students).

For universities, therefore, getting the programme right - attracting the right students - is a clear prerequisite for success. Understanding which comes first - chicken or egg - is crucial.

More broadly, the chicken and egg question is key to understanding a wide range of policy issues. Which causes which: class size or scholastic performance? risky behaviours of depression? investment or output?

Hilmer, M., & Hilmer, C. (2011). Is it Where You Go or Who You Know? On the Relationship between Students, Ph.D. Program Quality, Dissertation Advisor Prominence, and Early Career Publishing Success Economics of Education Review DOI: 10.1016/j.econedurev.2011.04.013