Over the last 20 years, support for legal abortion has continued to drop among young adults, a new Gallup poll shows. In 2009, only 24 percent of Americans aged 18 to 29 said abortion should be legal under any circumstances, a drop from 28 percent in the year 2000 and 36 percent in 1990. Even compared to 30- to 64-year-olds, the young cohort is now less likely to support abortion, the Gallup survey on Friday revealed.