Over the past several centuries, as the economic situation improved and stabilized, eliminating the need to marry off young girls to ensure their sustenance, the practice ceased to exist in most countries (AHS 37:33). Rather, marriages were generally arranged after girls reached halakhic adulthood and physical maturity, generally between the ages of thirteen and sixteen, and the final decision about whom to marry was left to them. The parents still had the very important job of helping their daughters choose a husband and of providing a dowry (approximately a tenth of their assets). However, the decision to get married was made by the girls themselves, and the kiddushin money was given to them directly.
Nowadays, thanks to a much higher standard of living and greater opportunities for women to utilize their talents in various fields, women are marrying later. There are two reasons for this. First, because women can now use their skills in many areas, they have a concomitant obligation to learn more Torah as they train in a suitable field, so that they can contribute goodness and blessing to the world. Second, in the past, young couples lived with their extended family, so even young women could have children because the older women would help them rear the children. In contrast, now that young couples set up house on their own, it is not realistic for women to get married until they are able to take full responsibility for caring for their children.
Nonetheless, women should not delay marriage too long. The right age for women to get married is slightly younger than the right age for men. First, girls mature earlier, as is reflected in their becoming obligated in mitzvot at the age of twelve, a year earlier than boys. Second, the mitzva to learn Torah requires less of women than of men. Third, women are not obligated to serve in the army as men are. It is true that nowadays, when it comes to supporting a family, women share the burden with men. One might think this would cause marriage to be delayed. On the contrary, it can enable earlier marriage. If a woman finishes her studies early, she can assume most of the burden of supporting the family at the beginning of the marriage, putting her husband through school where he can train in a suitable field, rather than needing to wait until he is able to support the family. In conclusion, the appropriate age of marriage today for men is between twenty and 24, while for women it is approximately two years younger.