Cost and standard of lighting

Assuming no decrease in the purchasing power of money, as much light can be purchased today for one or two cents as could be bought a century ago for one dollar. But unfortunately our dollar has had many shrinking moods during this period, and this must be taken into account in any comparison of lighting standards with those of a century ago. For the sake of comparison let it be assumed that the purchasing power of gold is only one-third as great today as it was one hundred years ago. If the use of light were keeping pace with the efficiency of light production, the workman would be supplied with three hundred times more light than he then had. But the standard of working conditions has also greatly altered. If it be assumed that this has increased about five times, the workman today should be supplied with about fifteen hundred times more light than he had a hundred years ago.