Changing the diversity in the profession can only be done by directing attention to the pipeline for new economists.
1) Every college economics program should post written curricular advice for all 1st to 4th yr college students to read. It is critically important that *advanced* curriculum advice (preparing for graduate economics programs) should be available even to the college FRESHMEN. Otherwise, currently underrepresented groups (women, first-generation college attendees, etc), get good advice TOO LATE to invest in accompanying courses in probability theory, mathematics, statistics, computer science, and sister social sciences (...and so on...)
2) Many female students defend their high Grade Point Averages by minimizing their *quantitative* course exposure. (Parents, are you listening?) The pioneering women who dealt with the glass ceilings of the world have been inadvertently handicapping their daughters by telling them they have to outperform "the boys"...It's all in the potential for MISINTERPRETATION of their well-meaning advice. Revise that advice: say rather, "Study hard and get good grades but NOT at the expense of NUMERACY." This is a profession that does indeed sneer at people with insufficient mathematics and statistics training. I have seen economists dish out rude comments those lacking such skills, in all fairness, in an even-handed way to all those lacking the tools they expect and missing insights those tools provide. The mechanism for changing DIVERSITY in the future? While it would be an interesting exercise to remove all rude economists, more realistically, giving young students of economics TIMELY advice to acquire the quantitative and analytic skills and the motivation to do so is more likely to have a direct effect. (If interested, further notes on training may be found here: https://www.tandfonline.com/doi/abs/10.1080/00220485.2017.1353467
3) I agree with answer posted by Julie_A_Nelson: the profession does not adequately reward attention to economic questions facing women. This also affects the number of women students in the academic pipeline. For half of the population, one would expect 50% attention in labor economics instruction, but most labor textbooks spends at most 20% of its content on what is arguably a MORE INTERESTING problem of female labor supply given competing interest for her productive time. (And I shouldn't have to mention that married female entry into the labor force accounts for a huge effect in market-valued GDP growth over the last century.) Do female economics students care? When I offered a labor economics class entitled "Women, Work, & Property Rights"* enrollment by gender was 2:1 Female:Male, which was unprecedented over multiple decades at our economics program. (*"Property Rights" because I also asked the students to consider the historical determinants of in women's participation in capital as well as labor markets.