We tend to date an innovation from the date a patent was filed or a machine unveiled, but a long time can pass between when something becomes technically possible and when the majority of people are using that thing. Electricity, for example, was a wonder technology of the 1880s, but it wasn't until the mid 1920s that a 50 percent of Americans were electrified. The telephone, which dates back to the 1870s, did not achieve 50 percent penetration until *after* World War II. Air conditioning wasn't a majority experience until 1973. Even cellular phones, which are the go-to example of rapid technology adoption, were first launched (in the guise of car phones) in the 1940s, and were well understood by the late 1970s.
Which is what makes these two graphics, one by Nicholas Feltron, the other by Karl Hartig, so fascinating. (They're hard to see in-line: click on them to make them bigger.) You may have seen them bouncing around the Interwebs.
They purport to show how fast technology moves, I see it the opposite way. If you were born in 1870, say, you heard about electricity as a kid, but were unlikely to get it until you were in your 50s! If you were born in 1960, you heard about computers as a kid, but statistically speaking, probably didn't have one until you were in your mid-30s.
