Are there any non-feminist objective studies that address the wage gap/glass ceiling?

Just curious, seems there is much disagreement on whether or not the wage gap or the glass ceiling exists, so i went looking for evidence of both and unfortunately all i could find were feminist based studies.

I do not mean to imply that these studies are in fact false, simply that there is a possibility of conflict of interest, the same would apply to masculist based research, and without comparing the research to objective viewpoints, how can one be sure of the existence?

So, does anyone know of any possible 3rd party or objective studies that research the possibility of the wage gap or the glass ceiling?