Final answer:
The decrease in teenage births in the United States is attributed to several factors, including comprehensive sex education emphasizing safer sexual practices and contraception, evolved societal attitudes towards sex and family structure, the greater use of contraceptives, and national preference for 'abstinence plus' sex education programs.
Step-by-step explanation:
The number of teenage births in the United States has considerably decreased from 50 years ago due to several factors. One of the most notable reasons for this decline is the shift towards sex education programs that emphasize safer sexual practices alongside or instead of abstinence, which is supported by most U.S. adults. The National Survey of Family Growth data indicates that society's sexual attitudes and acceptance of non-traditional family structures has evolved, which may also contribute to changes in teenage sexual behavior. Moreover, the accessibility and use of contraceptives have markedly improved, and there is a general trend towards fewer children in families, which align as well with the observed decrease in teenage births.
Although the type of sex education being taught in schools is a contentious issue, national surveys show most U.S. parents support sex education programs that incorporate both abstinence and sexual safety, widely known as 'abstinence plus'. Changes in public opinion regarding premarital sex and reproductive rights reflect a more open societal approach towards adolescent sexuality, suggesting a movement from strict traditional values to more practical and inclusive sexual education and family planning practices.