I have heard that over 30% of men will be bald by 30, and that 60% will be bald by 50. However, I hardly ever see a bald woman unless it is a story about a cancer survivor or someone going through cancer, meaning that they lost their hair through chemotherapy rather than natural balding. I do not understand why this is. I do know that women tend to have longer hair than men, so maybe their follicles are more active, preventing them from going bald. If someone could correct my explanation, that'd be appreciated.
Let's start off by saying that "baldness" is a very broad term... it includes not only hair loss but also miniaturization, which accounts for the majority of the phenotypic "baldness" associated with alopecia areata. While alopecia areata is not the only cause of baldness, it accounts for 4 out of 5 cases in men, whereas in women it only accounts for half.
The reason that it's more frequent in males is the presence of 5α‐reductase in the sebacious glands and the dermal papilla - this enzyme mediates the metabolism of testosterone into dihydrotestosterone. Dihydrotestosterone, in its turn, binds to androgen receptors and affects gene expression, speeding up the anogen phase. Consequently more hairs are in the telogen phase, and the hair is shorter. In severe cases, miniaturization can become actual hair loss.
Because males higher levels of androgens, there is more testosterone available to be metabolized in the follicles. Therefore, the incidence of alopecia areata (and consequently baldness) is higher in men than in women.
Piraccini BM, Alessandrini A. Androgenetic alopecia. G Ital Dermatol Venereol. 2014 Feb;149(1):15-24. PMID: 24566563.
Randall VA, Thornton MJ, Messenger AG. Cultured dermal papilla cells from androgen-dependent human hair follicles (e.g. beard) contain more androgen receptors than those from non-balding areas of scalp. J Endocrinol. 1992 Apr;133(1):141-7. doi: 10.1677/joe.0.1330141. PMID: 1517703.