Industrial Revolution: Machine knitting transformed the industry, while hand knitting became both a necessity for the poor and a leisure activity for the middle and upper classes. Women knitted socks and items for soldiers during wartime—particularly notable during both World Wars.

The cost of developing a fighter plane increased by a factor of 100 from the 1950s to the 1980s, which resulted in fewer new planes being built. In the 1950s, the American aerospace industry developed 49 planes; in the 1980s, that number had dropped to seven. Instead of working on 20 or more plane designs over the course of a career, an engineer... See more