"In 1996, Yale economist William D. Nordhaus calculated that the average citizen of Babylon would have had to work a total of 41 hours to buy enough lamp oil to equal a 75-watt light bulb burning for one hour. At the time of the American Revolution, a colonial would have been able to purchase the same amount of light, in the form of candles, for about five hour’s worth of work. And by 1992, the average American, using compact fluorescents, could earn the same amount of light in less than one second. That sounds like a great deal."
Via Society for College and University Planning (SCUP)
And the cheaper light gets, the more light we use. Maybe that's a good thing for higher education:
Many of the first treatises denying the existence of ghosts and witches came from larger cities in the Netherlands and England, which featured some of the earliest and most extensive street lighting in Europe.