For the seventh year in a row, the teen birth rate in the U.S. hit a record low in 2015, thanks to less teen sex, better birth control use, and more education, according to the latest data from the U.S. Centers for Disease Control and Prevention.

The U.S. still has higher teen birth rates than most industrialized countries, including Canada and the United Kingdom, but 2015 marks the 24th year in a row that the country posted annual declines. Since 2009, birth rates for girls aged 15-19 have reached a record low each year.

The number of births for teens dropped 8 percent from 2014 to 2015, to 22.3 births for 1,000 teen girls. Since 1991, the overall rate has declined by 64 percent, the CDC reported on Wednesday.

There are "a number of factors" contributing to the two and a half decades of declining birth rates, according to the CDC's new data. A basic reason for the recent drop is an ongoing trend in declining teen sex experience -- data from national surveys show sexual experience in teens has declined since the peak in 1988.

But for those who are engaging in sexual activity, the CDC says, the birth rate drop is linked to two things: more teen pregnancy prevention programs and the increasing use of what experts consider effective contraception methods, such as birth control pills and intrauterine devices (IUDs).

When it comes to birth control, more teens are using at least one method — with the numbers jumping from 78 percent to 86 percent between 2007 and 2012, according to a study published this year in the Journal of Adolescent Health that helped inform the CDC's data.

The most common contraception cocktail for teens is the birth control pill and condoms. Overall, the use of highly effective methods increased to 51 percent in 2009 and has remained steady in the years since.

Pregnancy rates dropped for teens in all race and ethnic groups, but disparities still exist. The highest numbers are seen among Hispanic females, with that group having 34.9 births per 1,000 teen girls in 2015 compared to whites (6.0 births) and Asian or Pacific Islanders (2.7).

The gap has narrowed from 77 births for Hispanic teens in 1991 compared to 27.3 that same year for Asian or Pacific Islanders, consistently the lowest-reporting ethnic group.