Unconscious bias toward recommendation letters written by men? This is an attempt to rescue a strongly down-voted question.

Are there any studies investigating possible unconscious gender bias in evaluating recommendation letters?  Specifically, is there any published evidence that recommendation letters with female authors are (or are not) less effective than recommendation letters with male authors?  Studies considering letters for graduate admission, faculty hiring, or promotion and tenure are all relevant.

Let me emphasize that I am not asking about intentional sexism, which I assume is sufficiently rare to be insignificant, but rather unconscious bias.  I am also not asking for anecdotes, but pointers to actual published literature.

Similar studies have revealed significant gender disparity in several related academic contexts, including recommendation letters for male vs. female applicants.  Other examples include:


Applications to lab manager positions
Prospective doctoral students emailing faculty
Judgement of publication quality
Teaching evaluations (See also)
Selection for mathematical tasks (See also)
I couldn't find any recent (written after 2000, that is) study that directly addresses the issue of how the recommender's gender influence how the letter is perceived. However, I did find one interesting survey study (doi: http://dx.doi.org/10.1111/j.1468-2389.2009.00453.x) that asked experts in personnel-related professions how they think about LORs. One item asked them to rate on a scale from 1 (strongly disagree) to 5 (strongly agree) the following statement:


  I believe that applicant, referent, or reader gender may influence how one interprets the contents of LORs


The average response was 2.86 with an SD of 1.22. About 42% strongly agreed, and 43% strongly disagreed. Clearly there is some level of controversy when it comes to the role gender plays in LORs. The study did not, however, ask any question directly about the referent's gender, which makes it even harder to draw any specific conclusion for our purpose here.