Scientific Research and Invention 121 
that “acceleration rather than structural change is 
the key to an understanding of our recent economic 
developments.” The committee added: “But the 
breadth and scale and ‘tempo’ of recent develop- 
ments gives them new importance.” 
What has happened is indicated by the fact that 
in the United States, eight million three hundred 
thousand workers produced in 1925 one-quarter 
more than nine million wage workers turned out 
during 1919. 
The new indexes of the Federal Reserve Board 
measuring industrial production record this gratify- 
ing advance which reflects an increase in the Ameri- 
can standard of living. The indexes cover, directly 
and indirectly, four-fifths of the industrial produc- 
tion of the nation—directly in about thirty-five indus- 
tries, and collaterally in many more. They were 
occasioned by the striking increase in recent years of 
the output of many industries. Thus the quantity 
of automobiles increased by 204 per cent between 
1919 and 1925; the output of petroleum refining 
advanced by 108 per cent; rubber goods by 59 per 
cent; glass by 78 per cent; cement by 101 per cent; 
brick, pottery and other clay products by 68 per 
cent; chemicals and acids by 36 per cent; paints and 
varnishes by 40 per cent; carpets and rugs by 38 
per cent; silk goods by 37 per cent; iron, steel and 
non-ferrous metals by 32 per cent; and various items 
of food, drink, and tobacco by from 6 to 51 per cent. 
The general volume of production had increased 
between 1919 and 1927, inclusive, by 46.5 per cent;