nitpick: nice graph on the "information superhighway" but a label about exactly what is being measured (0.000055%, of what) would be great. Is this a word count

nitpick: nice graph on the "information superhighway" but a label about exactly what is being measured (0.000055%, of what) would be great. Is this a word count? Or its rate of change? There's a reason our (stuffy) professors/sub-editors always insist on sources and accurate labeling. I'm only interested because the most recent data points, despite large decline, still suggest a non-negligible use of a term which I haven't heard in years other than in a small amount of anecdotes/jokes.