According to the Center for Disease Control the trend towards lower teen pregnancy rates has continued with only modest interruption since 1991 and was particularly pronounced in the eight years from 2006 to 2014 (the latest year for which data are available). "In 1991, the birth rate among females age 15 to 19 was 61.8 per 1,000. As of 2014, that number has declined to 24.2 per 1,000."
Birth rates are down a whopping 51 percent among Hispanics age 15 to 19 since 2006, and down 44 percent among black teens, according to a survey of census data by the Centers for Disease Control and Prevention. Teen pregnancy rates among whites also fell by a third.From here.
This has reduced racial and ethnic disparities in teen birth rates. Hispanic teen birth rates (38.0 per 1,000) are now about 9% more than black teen birth rates (34.9 per 1,000), which are in turn about twice the white teen birth rate (17.3 per 1,000).
Greater use of contraception and especially long term contraception has been an important factor in the change: "use of long-acting contraceptives like IUDs and implants jumped from 1 percent of teens a decade ago to 7 percent in 2014." But, teens are also simply having sex less often.
Abortion rates per teen pregnancy have been more or less constant during this time period (resulting in dramatically fewer teen abortions as a result).