Yearly Totals -->
The Depression is obvious; Wars (WWI, WWII, Korean) seem to
halt input somewhat. Big increase from 1955 to about 1975
then leveling with some decrease in early 80s (more fuel
efficient cars)
Solid Fuels -->
Rapid rise until 1910; then fairly slow rise until 1950;
1950-1970 slope significantly higher than 1910--1950 and
then a still higher rise occurs after 1970