They roughly halved, from an average of around 4½ per cent in 1980 to a bit over 2 per cent in the latest period. Notwithstanding its most recent uptick, the average margin now is well below where it was a few years ago.
Perhaps the most authoritative input to our understanding of technology is the diffusion of innovations theory developed in the first half of the twentieth century. It suggests that all innovations follow a similar diffusion pattern – best known today in the form of an “s” curve.