A) The Google search volume for the term “h-index” has increased rapidly since its introduction, owing to the popularity and relevance of this ranking index. (B) The ``predictive power'' of the regression model of the h-index, and h-index increments, for Physics disciplines across for different career age cohorts (years since first publication t = 5). Image: Aalto Univ.Models universities use to forecast scientists' future contributions are not as reliable as previously thought.

In a recent study, Aalto Univ. and IMT Institute for Advanced Studies Lucca researchers demonstrate mathematical analysis of past performance cannot reliably determine the future performance. This means that current models dangerously overestimate the predictability and should not be used for career advancement decision process.

"Based on our results, the predictability of current models for real application in recruitment decisions is questionable. Efforts to model future impact need to be aimed more directly at sapplications in the career advancement decision process," says Prof. Santo Fortunato from Aalto Univ.

In recent years it has become more common for universities to use quantitative measures for yard-sticking the productivity and impact of individual researchers to help reduce hiring risks. Models thought to be capable of foreseeing a scientist’s future impact by way of his or her future “h-index” have become a common tool in recruitment decisions as well as other scientific evaluation, advancement and reward processes.

Scientists concluded that great caution should be taken when attempting to forecast an individual's future based on their h-index. Specifically the authors show that it is easy to grossly overestimate the predictability of cumulative measures over a person's entire career.

The study analyzed 762 scientists from three disciplines: physics, biology and mathematics. By applying future impact models to these careers, a number of subtle, but critical, flaws in current models were identified. Specifically, the h-index contains false autocorrelation, resulting in a significant overestimation of “predictive power.” Moreover, the predictive power of these models vary greatly with the career age of scientists, producing least accurate estimates for already risk-burdened early career researchers.

Aalto researchers concluded that care must be taken to select the correct measures and methods to evaluate scientific candidates in the future. Increased attention should be paid to the potential shortfalls of quantitative methods when applied to the decision-making process.

The results were published in the Scientific Reports, a research publication from the publishers of Nature.