From the NYT:
Potty parity does not always mean that there will be the same number of toilets for women and men. Parity is measured by wait times.
Studies show that women take about twice as long as men in the restroom. The reasons vary, from the obvious (the need to secure themselves inside a stall, shed more clothes and use toilet paper) to the not-so-obvious (menstrual cycles and the increased likelihood, compared to men, of ushering small children).
Groups including the American Restroom Association and the World Toilet Organization view quick access to clean public toilets as no laughing matter. People with medical problems, including bladder or bowel dysfunction, may not be able to wait. Long waits can exacerbate other issues, including urinary-tract infections.
For years, women have most dealt with the consequences, if not the indignity, of waiting in long lines.
New York City passed a law in 2005 requiring that all new or significantly renovated places of public assembly — concert halls, arenas, Broadway theaters, stadiums and the like — have two women’s toilet fixtures for every one devoted to men. About half of the states and many municipalities have similar laws, with varying ratios, designed to offset the extra time that women take in the restroom and slowly undo decades of male-dominated design and construction.