That's not really true, You just weren't paying attention. There has been continuous improvement over this period as well as quite a bit of genuine innovation, some of which has made people large amounts of money. Even for boring incandescent lamps you'll find that todays lamps last longer for equivalent performance than their 70 year old counterparts.Valuethinker wrote: Having been more or less static for 70 or so years, in the last 10 years lightbulbs have just taken this extraordinary leap in efficiency.
Some highlights of the last 70 or so years:
1959: Tungsten Halogen bulb on the market
1964: Metal halide lamps introduced at worlds fair
1965: Practical high pressure sodium lights on the market, these would be continually improved for the rest of the century.
1970s: electronic ballasts for fluorescents, also rapid start ballasts.
Mid 1970s: Compact Fluorescent invented
Early 1980s: CFL on the market
1987: Ceramic filament incandescent lamp invented.
1993: I bought my first CFL (although it is almost the size of a softball so "compact" is relative)
1996: Sulphur lamps and light pipes used in Smithsonian Air and Space Museum