I am reading an article at which authors used an effect size that it's totally new to me and I do not know how to interpret it. I would appreciate if anyone could explain its meaning or provide any reference about its interpretation. Below, I paste some sentences from the original article at which the authors' explain how data were analyzed, highlighting in bold the effect size description.

We used linear regression model (...) Analytically, we regressed one of the outcomes on the indicator for opposite sex (β) and the set of control variables (

**λ**). C In the main regressions, the estimate on opposite sex (β) compared the mean outcomes between females exposed to a male and females exposed to a female. Figs 1 and 2 plot effect sizes, that is, t

**he point estimate divided by mean of an outcome in the estimation sample**

My questions are: 1) why beta (which I assume is the standardized regression weight) was divided by the mean of the estimation sample?; 2) Would not have been better just to use the b (unstandardized) weights as a measure of effect size (or to divide b by the SD of the sample to have an approximation to Cohen's d)?

Thanks in advance for any answer