Unlike their male counterparts, the amount of material used in female underwear has been steadily decreasing over the last number of centuries. Indeed, so much so that, short of going commando, this trend unfortunately can not keep continuing and must level off. Thus, we are left with an exponential decrease, as shown in the graph above. For direct comparisons with men, bras are not included in this treatise, despite the growing number of men who need them!
Back in the middle ages, a potential suitor would need a machete to hack through the layers of chemises, smocks, petticoats and the like that a woman used as underwear. This cornucopia of genital attire possible doubled as a chastity belt of sorts! By the early 1900s, this mercifully had been whittled down to mere bloomers. The trend continued through to bikini style briefs and the g-string - surely the acme of female underwear design!!!
I have noticed that the string nature of modern women's underwear would appear to the untrained male eye to be giving them constant wedgies! While this would seem to be most uncomfortable to a man, the absence of "undercarriage" does have to be factored in! Unfortunately, most of this empirical evidence has been gathered from VPL (visible panty lines) and not, err, investigations in the field!