"IDK. I Don't Know." It's a catch-all phrase, but ask an Internet Pioneer a question and his or her response is typically preceded by a disconnected or even semi-perturbed, "I don't know…" followed by a reasonably thoughtful response. Try it. Ask an 18- to 22-year-old questions about politics, issues, their future, their friends and there's a high probability his or her answers will be interspersed with "I don't know." The short-form text version is the popular IDK.
I don't have all the numbers, but The Walking Dead midseason finale Sunday night was seen by 12.1 million viewers. 7.7 million were adults 18-49. Down quite a bit from the season premiere of 16.1 million viewers but net/net still up 29% when looking at year over year.