It does not say: "...only 12 percent of Americans 16 years and older have been with their current employer for more than ten years." It says 12% stay between 10 to 14 years, another 6% for 15 to 19 years and additional 11% stay for more than 19 years. So it sums up to 12 + 6 + 11 = 29% of Americans 16 years and older that have been with their current employer for more than ten years. That's almost thrre times more!