The graph also shows things like the mobile phone as invented in 1983 and the internet as 1991. These years would be fine within the context of when those technologies became commercially available to a larger group of Americans. But radio and TV weren't commercially available in 1897 and 1926 respectively. Do you see the problem?If you want to say that the invention of television occurred in 1926, then you don't get to say the internet was invented in 1991. The privatization of the internet in the early 1990s and the introduction of the web did indeed make it available to the broader public. But if we're playing by the same rules as radio and TV, we'd have to put the invention of the internet at 1969, when the first host-to-host message was sent from UCLA to Stanford, breathing life into the Arpanet. And as for the mobile phone, you'd have to peg its invention at something closer to the mid-70s, not 1983.