Final answer:
Adolescent pregnancy rates have decreased since 1990 due to increased educational support, decreased child marriage, and better access to reproductive health services.
Step-by-step explanation:
Since 1990, rates of adolescent pregnancy have significantly decreased. This decline can be attributed to a variety of factors, including increased support for girls' education, decreased child marriage, and the promotion of reproductive health services. Efforts to educate young people about sexual health and contraception have played critical roles in reducing teen pregnancy rates. Moreover, this trend is consistent with the broader patterns of societal changes such as the increased median age of first marriage for both men and women, indicating shifts in personal and economic priorities.