Women were half as likely as men to receive excellent-rated recommendation letters for geoscience postdoctoral fellowships at a competitive university in the northeastern United States, reports a study published online in Nature Geoscience. In addition, it made no difference whether recommenders were male or female, suggesting that unconscious gender biases affect men and women equally.

In the geosciences, women hold about 40% of all doctoral degrees, but among full professors they represent only 10% of the workforce. The postdoctoral years have been identified as the largest leak in the pipeline for female scientists.

Kuheli Dutt and colleagues analysed a data set of 1,224 recommendation letters for highly selective geoscience postdoctoral fellowships, written by 1,101 recommenders from 54 countries for 452 applicants, and specifically rated the length and tone of the letters. They found that, after controlling for recommender region, recommender gender and letter length, female applicants were only half as likely to receive an excellent, rather than a good letter of recommendation. Although the authors were not able to control for the qualifications of the applicants, they note that roughly the same proportion of men and women received letters that were rated as doubtful, and these doubtful ratings represented only 2.5% of all letters.

The authors conclude that women are disadvantaged from the start of their geoscience careers and hope that their results will help raise awareness of these gender biases and inform initiatives to recruit and retain women in science, technology, engineering and mathematics.