It's a startling idea, but an incorrect one. The percentage is almost certainly much higher than that.
Using somewhat subjective definitions of "at war" -- Korea counts but Kosovo doesn't in our analysis, for example -- we endeavored to figure out how much of each person's life has been spent with America at war. We used whole years for both the age and the war, so the brief Gulf War is given a full year, and World War II includes 1941. These are estimates.
But the beginning of the conflict in Afghanistan in (late) 2001 means that anyone born in the past 13 years has never known an America that isn't at war. Anyone born after 1984 has likely seen America at war for at least half of his or her life. And that's a lot of Americans.
These figures shift easily. An end to the conflict in Afghanistan (and, if you include it, the overlapping fight against the Islamic State) means that the percentage of time those young people have lived in a state of war will decline quickly.
But that state of war, we are told (I am too young to know better) feels different than America during World War II or, particularly for the college-aged, Vietnam. Moreso than those wars, war today is distant, fought on our behalf.
That's Raddatz's other, perhaps more important point: Young Americans have lived in a country at war for almost their whole lives, but they have to be reminded of it.